1 Introduction
In the medieval Latin question commentaries on Aristotle’s De somno et vigilia, one of the standard quaestiones asks whether plants are capable of sleeping and waking. The question goes back to Somn.Vig. 1, 454b27–455a3 where Aristotle rules this out. Aristotle has laid the basis for this claim already in the De anima and again in the beginning of De somno et vigilia, where he states that the nutritive part of the soul can exist without the sensitive but not vice versa.1 Plants are ensouled beings that have only the nutritive soul, and in Somn.Vig. 1, 454b27–455a3 Aristotle concludes that since plants, contrary to animals, lack sense-perception, and since sleep is the immobilisation of sensation, plants lack also the capacity to sleep and wake. He adds two observations as further support:
By contrast, no plant can partake of either of these affections. (i) For neither sleep nor waking belongs to anything without perception, whereas things to which perception belongs can also have pain and pleasure. And what can have these can also have appetite. But none of these belongs to plants. (ii) Proof of this is the fact that the nutrient part performs its function more during the sleeping than the waking state. For more nutrition and growth take place at that time, suggesting that nothing is needed from perception to further those ends.2
Aristotle’s claim that plants are incapable of perceiving and, hence, also of sleeping and waking, may at first glance seem clear-cut and unproblematic, but the medievals found several reasons to debate it, one no doubt being the compelling empirical evidence that plants, like animals, display a variation in levels of activity at certain intervals. The claim also presupposes the assumption of several differences between the natures and functions of the nutritive and sensitive souls that warrant further investigation. Furthermore, the fact that the Westerners were well aware of the ancient debate on the matter no doubt contributed to the medieval interest. Via the Pseudo-Aristotelian De plantis, which had been translated from Arabic into Latin by Alfred of Sareshel around 1200,3 it was well known that Plato, among others, had claimed that plants have sensation.4 The De plantis begins with an overview of the ancient debate on the question, which is explicitly linked to the question of whether plants can sleep and wake, and the first chapter is almost entirely devoted to this problem.5 In the end, however, the most cogent reason that the question of absence of perceptual capacity in plants became a standard topic in the medieval tradition is clearly that from the commentators’ perspective it puts Aristotle’s definition of perception to the test. The present chapter aims to demonstrate how the medievals identified a number of crucial questions generated by Somn.Vig. 1, 454b27–455a3 that must be answered in order for Aristotle’s claim about the complete lack of perceptual capacity in plants to fit with his overall theory of perception.
2 Albert the Great
The earliest known medieval Latin commentary on Aristotle’s treatises on sleep and dreams is the commentary by Adam of Buckfield (c.1220–before 1294), dated to between the late 1230s and early 1240s.6 If a date towards the end of this period is correct, Adam’s commentary appeared more or less at the same time as Albert the Great’s (1206/7–1280) exposition of Somn.Vig. in De homine, which was finished around 1242.7 There is no clear indication that Albert used Adam’s work, and in the case of Somn.Vig. 1, 454b27–455a3 Adam’s commentary contains little more than a paraphrase of Aristotle’s text.8 Albert’s De homine, on the other hand, contains the earliest known proper discussion of Aristotle’s claim that plants cannot sleep or wake because they lack sense-perception. Here, Albert’s exposition of Aristotle’s conclusion in Somn.Vig. on the lack of sense-perception and sleep in plants is not yet systematised as a separate problem, but addressed as part of the question whether sleep and waking are affections of sensation.9 For Albert’s main point, which is the affirmative answer to this question, Aristotle’s observations in Somn.Vig. 1, 454b27–455a3 come in handy as proof that sleep is not an affection of the nutritive soul, but of the sensitive.10 For further defence of Aristotle’s claim that the nutritive soul is even more active in sleep, Albert turns to Averroes’ Compendium,11 where Averroes argues that the fact that both irrational animals and human beings are in possession of their sense-organs in sleep while at the same time they do not perceive or move in sleep12 proves that in the sleeping state the sensitive power of the animal withdraws from the sense-organs into the body. Albert concludes:
The meaning of this authoritative statement is that sleep is proved to be an affection of perception by the fact that plants do not sleep whereas brute animals and human beings do, and the latter two have nothing else in common but the sensitive soul. And since only the external senses, and not the interior, are immobilised in sleep, sleep is an affection of the external senses and not of the interior.13
2.1 A Soul in Continuous Operation
In this connection, Albert raises a number of counterarguments to the claim that sleep is only an affection of the sensitive soul and not of the nutritive. The first of these became one of the most debated problems among Albert’s successors with regard to the interrelation of perception and sleep, because it presupposes a fundamental difference between the sensitive and nutritive soul. Albert here refers to Somn.Vig. 1, 454a26–32, where Aristotle explains why no animal can be always asleep or always awake:14
For all things that have a natural function must, whenever they exceed the time for which they can do a certain thing, lose their capacity and cease from doing it, e.g., the eyes from seeing. It is the same for the hand and everything else that has a function. So if percieving is the function of some part, then this part too, should it exceed the due time for which it is capable of perceiving continuously, will lose its capacity and will do so no longer.15
Since the nutritive power also, Albert claims, has a function that is limited by nature, the plant also must rest, and the living being’s rest from its natural function is sleep. To solve the apparent contradiction between this argument and Aristotle’s claim, Albert argues in response that unlike animals, plants do not need rest. While it is true, Albert grants, that every agent that acts finitely acts within a limited time, not all agents that act finitely also have the capacity to continue acting after its limit; only an agent that acts “with effort and suffering” can do so:
As to the objection that sleep is an affection of the nutritive soul, it must be said that it is true that every finitely acting agent acts with respect to some determinate time, but not every finitely acting agent has the capacity to exceed it. The Philosopher states that an agent that performs its function with effort and suffering has the capacity to exceed its time; when it exceeds the limit of its ability to continue operating, it will become tired and need rest in order not to be destroyed.16
Albert here seems to be loosely referring to Aristotle’s remark in Somn. Vig. 1, 454a26–b9 that the parts of the animal will become exhausted if they exceed their capacity and cease to function.17 Albert points out that this includes the sensory apparatus.18 But the sensory organs and the organs of motion exceed their capacity in different ways: the body gets tired by moving in directions opposite to that which is natural to its matter. Hence, moving a leg or an arm upwards will exhaust the organs of motion,19 whereas it is not movement but excessive stimuli that exhaust the sensory organs.20 In both cases, when the natural limit of the body’s capacity has been exceeded, it is necessary for the body to sleep. But for the nutritive soul, Albert claims, the conditions are very different: the activities of the nutritive soul are performed not by means of various bodily organs but by means of natural heat (calor naturalis) as its only tool (instrumentum).21 Since there is in this case no contrary relation between the nature of the instrument and the operation of it, living beings that have only the nutritive soul cannot exceed the limit of their capacity.22 Albert does not discuss the difference between exhaustion from motion and from sensation here; the difference between the process in the case of the organs of motion in the animal and the flow of natural heat in plants is clear enough, but the difference between the latter and the exhaustion of the sensory apparatus much less so. Albert here adds a peculiar alternative explanation of how the sensory organs are worn out: “some” claim that the sensible power finds sensing enjoyable and so goes on sensing for longer than it ought to. Albert dismisses this explanation on the rather dubious grounds that, of the two explanations, the former is closest to the truth because it agrees with the theory of exhaustion from motion.23
Albert’s second exposition of Somn.Vig. in his commentary on the Parva naturalia develops the question of the absence of perception in plants further.24 Here, Albert repeats his claim that the animal body becomes exhausted from moving in a direction contrary to the nature of its matter, whereas the activities of the nutritive soul are of a different nature and, unlike locomotion, do not cause the living being to exceed the limit of its natural capacity. He adduces a more elaborate form of his explanation in De homine: unlike locomotion, the motion involved in the activities of the nutritive soul, viz. nutrition, growth, and generation, is not contrary or violent, but natural in relation to the nature of the matter of the body. Nutriment moves not with effort, but naturally (naturaliter) to its destination, and nutriment, in turn, is the cause of both growth and reproduction. Hence, the motion in this case, viz. the flow of the nutriment, which Albert defines as a non-violent traction,25 does not result in exhaustion of the living being, but in its perfection.26
Albert is well aware that there is a wealth of empirical evidence to suggest not only that plants respond to external stimuli but also that they display different activity levels at certain intervals. In his commentary on Somn.Vig., he adduces as visible proof of the alternating retraction and expansion of the vital spirit in the plant that flowers open at dawn and close at dusk.27 Albert here provides a peculiar argument in support of the opposing position: it is a property of the sleeping body that it is smaller than the waking;28 hence, the opening and closing of flowers is empirical evidence that plants also sleep and wake. Albert refutes the argument by claiming that it is not sleep that causes bodies to shrink and flowers to close, but low temperature.29
Not only the opening and closing of the flower could result in the erroneous conclusion that plants sleep and wake; the fact that some plants blossom during summer, wither in winter, and bloom again in spring, could also be mistaken for an alternation between activity and rest identical to the cycle of sleep and waking in animals. When later expounding on the alternation of sleep and waking in animals in his commentary on Somn.Vig., Albert explains the mechanisms reflected in Aristotle’s statement in Somn.Vig. 1, 454a29–32: not only locomotion but also perception necessitate sleep in animals. The spiritus is reduced through the activities of the waking body; in sleep, the spirit is withdrawn from the external organs and returns to the inner parts of the body where it is restored and wherefrom it can then again expand.30 Since, according to Albert, an analogous circulation of the spirit takes place in plants, he needs to explain why the flow does not necessitate rest in the case of the plant. His explanation is far from convincing: since the matter of plants is both hard and moist, the spiritus can move only with great difficulty and, hence, the flow in the plant is much slower than in the animal; the cycle of the flow of the spiritus in the plant takes the whole year, with the spiritus flowing outwards during summer and withdrawing again in the course of winter.31 One would have imagined that the assumption of a higher resistance in the plant would result in exactly the opposite conclusion, that is, that the flow of the spiritus in this case would cause an even greater need for rest than in the animal. Instead, Albert’s account does not contain any explanation of why the mere fact that the cycle is longer in the plant than in the animal entails the conclusion that plants have no need for sleep whereas animals do, nor does he explain how the plant, without perception of the external world and of time,32 distinguishes between summer and winter.
It is clear, then, that nutrition, growth, and reproduction, do not cause exhaustion in the plant according to Albert, but it is equally clear that plants, as all other living beings, die at some point. In plants, the natural heat, without which the soul cannot operate, is sustained by the plant’s digestion and a suitable temperature in its environment. When nutriment enters the plant body, it has a cooling effect, which prevents the heat from burning out.33 The natural death of the plant occurs after a determinate time when the body is no longer capable of cooling the natural heat:
Violent death or destruction is the extinction or waning of the heat (for destruction may occur from either of these causes), but natural death is the decay of the same due to lapse of time, and to its having reached its appointed end. In plants this is called withering, in animals death. Death in old age is the decay of the organ owing to its inability to cause refrigeration because of old age.34
But is there no connection between the plant’s eventual inability to cool the natural heat and exhaustion of the nutritive soul over time? To my knowledge, Albert does not address this question in any of his works, but on the other hand, Aristotle does not seem to provide a clear answer to it either. Generally, plants are more long-lived than animals, since, even though they are dry and earthy, they are more moist than animals and do not dry out as easily (Long. 6, 467a6–11). Hence, Albert’s observation that the cycle of the natural heat is much slower in plants than in animals seem to have some support in Aristotle. It would seem that Albert understands the process in plants as both slower and weaker, in the sense that less spiritus is consumed and the need for rest is accordingly less. However, none of the arguments adduced by Albert demonstrate that the need for rest in plants is non-existent.
2.2 Feeding without Taste and Touch
Albert’s treatment of the question of plant perception in his commentary on Somn.Vig. not only elaborates on the theory of the nutritive soul’s lesser need for rest, further arguments are also added. If food is perceived by taste and touch,35 and the power of nutrition belongs to the nutritive soul, would that not imply that plants must also have taste and touch? Isaac Israeli is here mentioned as holding such a position:
And this is what the philosopher Isaac the Israelite claims in his work On the Elements when he distinguishes between two different types of touch and two different types of taste. For he says that some [living beings] have these senses only naturally (naturaliter) and some have them both naturally and in the way of an animal (animaliter); he says that those have them naturally that feed only with respect to substance, whereas those that feed with respect to substance and also have the capacity to receive the sensible species of the food, feed also in the way of an animal. From this argument it follows that plants seem to have these two senses, and it then follows that plants have sleep and waking.36
Albert’s reference is to Isaac Israeli’s De elementis, which was accessible to the Westerners in Gerard of Cremona’s (c.1114–1187) translation. Here, Isaac, on the basis of a number of empirical examples, concludes that plants have sensation because they are attracted to substances that are good for them and avoid those that can harm them. Plants are natural living beings, and thus the type of sensation they have is a sensus naturalis, whereas animals have, in addition to the natural sense, the higher sensus animalis, which includes, according to Isaac, the capacity to feel pain and to move by one’s own will. Hence, Albert’s rendering of Isaac’s position is somewhat misleading; Isaac clearly states that plants find pleasure in what is good for them and avoid what is contrary to their nature, and so the claim that it is only living beings that feed animaliter that can perceive their food finds no support in Isaac. In Isaac, the capacity to distinguish between good and bad nutriment appears to be a power shared by plants and brute animals (human beings, who in addition to perceiving naturaliter and animaliter also have the superior intellectual sense, the sensus intellectualis).37
The decisive point for Albert in his commentary on Somn.Vig. is that Isaac’s conclusion relies on an erroneous definition of perception. Albert concludes: to perceive is to receive the sensible forms without the matter, a capacity that belongs exclusively to the sensitive soul.38
Albert’s refutation of Isaac’s conclusion can only be properly understood in light of Aristotle’s de An. 2.12, 424a32–b3:
And it is evident also why plants do not perceive, although they have a soul-part and are affected in a way by tangible objects; for instance, they are both cooled and heated. The reason is that they do not possess a mean, that is, the sort of principle that receives the forms of perceptible objects; rather, they are affected together with the matter.39
Plants have no sensitive power and, hence, no way of meeting the definition of perception in de An. 2.12, 424a17–19, viz. to receive the form without the matter,40 but plants can be affected – and changed – by the matter of sensible bodies.
The ultimate reason that plants cannot sense is their composition; perception requires, according to Aristotle, a compound composition. Plants are, just like bones and hair, living substances but have no sensation because they are mainly composed of earth and, hence, too simple.41 But what exactly does it mean that the plant receives the form together with the matter? Albert’s exposition in his commentary on Somn.Vig. is in this case surprisingly scant. His example of the plant’s reaction to temperature changes and Aristotle’s example of hot and cold in de An. 2.12, 424a33–34 do not trigger a further explanation from a philosophical perspective. Also his commentary on De anima contains little of interest in the matter and no answer to the question that concerns us most: sensible objects also act on plants with both form and matter, but because of their simple composition, plants cannot perceive, but can only be affected by a “material affection” (passio materialis, as opposed to a passio formalis). Hence, plants can be changed by the matter, but not by the form only; for instance, in the case of taste plants can feed and be changed by the matter of the nutriment, but they cannot judge the flavours,42 for instance, they cannot discriminate sweet from bitter.43
Albert discusses the distinction between sensing materialiter and animaliter at greater length in his commentary on De plantis and elaborates extensively – and apparently independently – on the view reported by Isaac:44 according to some, plants have the two senses that do not require an external medium, but operate “within” the living being (per medium intrinsecum), viz. taste and touch. These are, in turn, present in the plant and the animal in different ways. The theory represented by Isaac is here explicitly adjusted to the Aristotelian definition of perception: to sense animaliter is to receive the form without the matter; to sense naturaliter is to receive sensible qualities by a material change:
They say that a living being has sensation in the way of an animal when it has it in respect of actions and affections belonging to the soul only, and this is the capacity to judge and receive the sensibles; this only the soul performs when it receives the impression of the signet ring without receiving the gold or the matter of that signet ring. On the other hand, they claim that to have sensation by nature is to receive the sensibles through the action of the qualities of the matter and the material being that they have in their matter externally, as heat is in the hot and sweetness is in what has been infused with a sweet substance, and so on, because through this nature of the agent and the affected it is clear that the sensible is in a material and natural being.45
But if the plant can only be affected by the matter with the form, is there then any difference between this material change of the plant and the acting of a sensible object on an inanimate being? Yes, Albert replies on behalf of the theory’s proponents, because what acts and is affected by the tangible and tasteable object in the plant is still the soul, which informs all the body’s activities.46
Interestingly enough, Adam of Buckfield’s commentary on De anima discusses the distinction between the sensus naturalis and the sensus animalis ascribed by Albert to Isaac, but Adam does not refer to Isaac, and his line of reasoning deviates somewhat from both Isaac’s and Albert’s. When expounding Aristotle’s de An. 3.12, 434b22–24, where Aristotle concludes that taste and touch are essential capacities for the animal’s survival, Adam states that plants only feed on what is good for them because they feed only by nature. Animals feed not only by nature, but also by will, and since will can lead the animal to food that is either good or harmful, the animal needs the capacity to distinguish the former from the latter in order to survive, whereas, in contrast, the absence of will in plants makes the absence of taste and touch unproblematic.47
The question of appetite and desire in plants is a key problem already in De plantis. The work reports how Anaxagoras, Empedocles, and Plato, among others, claimed that plants have desire,48 but the author, following Aristotle, objects that desire can only exist with sensation.49 Albert elaborates on this conclusion in his De vegetabilibus, arguing that without sensation living beings are unable to discern what is desirable and, consequently, cannot have desire.50 But if the plant is incapable of desire, would that not mean that it is also incapable of distinguishing between good and harmful food and of pursuing the former and avoiding the latter? Obviously, Adam’s solution that plants by nature feed only on what is good for them does not hold empirically. In his question commentary on De animalibus, Albert, taking as his starting point Aristotle’s de An. 3.13, 435a17–b1, claims that plants have sensation in the first actuality and the power to absorb nutriment that is appropriate and reject what is harmful, but still lack the ability to perceive because they have no sense-organs:
To the first argument, it must be said that bones have the first actuality of sensation, because life is diffused in all parts of the body and so is sensation. But the second actuality [of sensation] exists only in the sense-organ. Hence, because of the first actuality of sensation and life, bones have the power to discern the appropriate and expel the noxious, and still they have no sensation. And for this reason, one can say that the plant has the power to receive the appropriate and expel the noxious, and still it has no sensation.51
This is puzzling in several ways. According to Aristotle, perception requires a sense-organ and an external object.52 Hence, it is surprising that Albert states that perception in the first actuality exists in the plant. Furthermore, if the plant’s ability to distinguish between appropriate and inappropriate food does not require perception, but is a power of the nutritive soul, why then would animals, as stated by Aristotle,53 need perception to survive? The fact that plants are stationary whereas (most) animals are capable of voluntary progressive motion is, just as Adam claims, an important part of the explanation, but if not by sensation, by which power does the plant separate appropriate food from inappropriate if that is at all within the plant’s capacity? Considering the fact that it is an easily observed phenomenon that plants grow towards favourable conditions and away from unfavourable ones,54 what separates plants from stationary animals in this respect?
To sum up at this point, Albert raises several questions related to Aristotle’s conclusion that plants have no sensation, but provides us with answers that are far from satisfactory. Albert’s explanations of the continuous operation of the nutritive soul are hardly persuasive, and his arguments and conclusion in the discussion on whether plants have the ability to distinguish between good and bad nourishment even weaker, but, perhaps most importantly, Aristotle’s compressed statement that plants receive the matter together with the form (de An. 2.12, 424b3) does not get any clearer in Albert’s account. In the latter case, however, Albert is perhaps not the only one to blame. As noted by the editors of the Cologne edition of Albert’s commentary on De anima, Albert is not using any of the known available Latin translation of de An. but an older translation from the Arabic,55 and the lemma in Albert’s commentary contains no literal Latin rendering of Aristotle’s
3 The Tradition after Albert
3.1 Albert’s Successors on the Continuos Operation of the Nutritive Soul
All arguments quod sic and quod non and corresponding refutations found in Albert live on in his successors, but some modifications and additions worth mentioning are made along the way. I have studied seven question commentaries on Somn.Vig. dating from the mid-thirteenth century to the mid-fourteenth: Geoffrey of Aspall (early 1260s),58 two commentaries in the MS Rome, Biblioteca Angelica 549 (one anonymous (1270–1300?)59 and one tentatively ascribed to Siger of Brabant (c.1250–70)),60 Peter of Auvergne (1270s),61 Simon of Faversham,62 John of Jandun (1309),63 John Buridan (c.1300–c.1361; date of the commentary unknown).64 I have also checked the expositio by Walter Burley (probably first decade of the fourteenth century)65 and, for comparison with a later work, the question commentary by John Versor (1443).66 In the earliest of the works studied, the commentary by Geoffrey of Aspall, the problem of plant perception is, as in Albert’s commentary on Somn.Vig., discussed as part of the larger question of whether the capacity of sleep and waking is found only in living beings that have sensation. In the vast majority of the later commentaries, however, the question whether plants have sensation is typically treated either as a separate question under this particular heading or as part of the question on whether plants are capable of sleep and waking. Several of the commentaries also include both questions.
As pointed out elsewhere, Geoffrey of Aspall’s commentary is of particular interest in that his work displays no clear indication that he knew of Albert’s work.67 Geoffrey’s discussion of plant perception is no exception, but if the conclusion that he has not seen Albert’s work is true, the few similarities between both treatments of the problem must be seen as an indication of a dependence on common source material. Unlike the other works here studied, Geoffrey’s discussion of the problem of whether only animals sleep and wake includes a comparison not only with plants but also with supralunar bodies and separate substances. For the two latter categories, Geoffrey argues that they have intellect but not sensation and, hence, they cannot be claimed to wake or sleep.68 For plants, the only clear parallel between Albert’s and Geoffrey’s discussions is the objection that not only the sensitive but also the nutritive soul needs to rest from its operations. Whereas Albert takes great pains to adduce several reasons why the activities of the sensitive soul but not those of the nutritive generate a need for rest, Geoffrey restricts himself to a categorical statement that plants operate without rest. Geoffrey’s main problem is instead Aristotle’s observation in Somn.Vig. 1, 454b32–455a1 that the animal’s nutritive faculty is more active in sleep than in waking. This claim, Geoffrey explains, does not apply to plants, but refers to a certain accidental property of living beings that have sensation. When such beings sleep, the spiritus withdraws from the external senses, which leaves these immobilised, and moves inwards where it instead fortifies the digestive process; hence it is not sleep itself that enhances digestion, but only the particular way that the spiritus behaves in living beings endowed with a sensory apparatus.69 Furthermore, in the animal, sleep is not caused by digestion itself, but by evaporations arising from the digestion of food; since the nutritive process in plants does not involve this phenomenon, the argument that sleep is needed for the digestive process per se does not hold.70
The discussion in Albert about the ability of the nutritive soul to operate continuously is found in some form in all the commentaries here studied.71 The question commentary ascribed to Siger of Brabant takes the argument several steps further, mainly by adding arguments for why the nutritive soul must be constantly active. Siger(?) refers to Averroes’ claim in his Long Commentary on De anima, 2.136.46–47 that the nutritive soul is always in its “final perfection,” that is, always fully actualised, whereas the sensitive soul need not be actualised all the time.72 Averroes cannot mean that all the functions of the vegetative soul are constantly in their second actuality; the plant can hardly be claimed to be constantly growing or constantly reproducing, and Siger(?) clarifies that it is the body’s nourishing itself that is constant:
Furthermore, it [the nutritive soul] acts continuously for the survival of the animal, which is a mixture of contraries, and a continuous action of contraries generates a continuous loss, and so some power is needed to continuously restore this continuous loss. But it is not necessary for the animal to perceive constantly in order to survive; therefore, etc.73
Hence, both the operation of the nutritive soul and that of the sensitive soul are important, but, unlike the nutritive, the sensitive does not need to be constantly active in order for the animal to survive, because the animal does not need to feed all the time. The cessation of the operation of the sensitive soul in the animal means sleep whereas the cessation of the operation of the nutritive means the death of the living being.74 But in addition to this difference, the sensitive soul also has a greater need for rest, according to Siger(?), because it is a passive power:
Every [animal] can cease from the act of sensing, and the reason for this is the following: the nutritive power is purely active. Taste and touch are kind of active, but the passive powers [of the soul] are sensitive. That whose operation consists in being acted upon requires more recovery and rest than that whose operation consists in acting.75
The same argument is found later in Simon of Faversham, who elaborates on it and also clarifies that the eventual exhaustion of the sensitive soul is not due to exhaustion of the sense itself but of the sense-organ. To prove his case, Simon refers to de An. 1.4, 408b21–22, where Aristotle proves that aging is due to an affection of the body and not of the soul by adducing the hypothetical example that if an old man acquired the eye of a young man, his visual capacity would be as good as the young man’s.76 Walter Burley also refers the sensitive soul’s greater need for rest to the presence of sense-organs: the more widely diffused the spirit is in the body, the weaker it becomes. In the animal, unlike in the plant, the spirit is distributed between the various sense-organs and, hence, less concentrated and burns out more easily.77 John of Jandun contrasts this refutation with Albert’s explanation that the animal’s forward motion, unlike the natural motion of the nutriment, is contrary to the nature of the body and hence generates a need for rest. “Some,” John claims, dismiss Albert’s theory as self-contradictory, and he does not make any attempt to come to Albert’s rescue:
But some disapprove of this, because it is certain that in the operation of nutrition some consumption of the spirits must occur. Furthermore, nutriment by nature moves downwards, but in the nutritive process it moves in all directions. Hence, it appears to move contrary to its natural inclination, wherefore it would seem that the nutritive process needs to rest for the spirits to recover sufficiently.78
3.2 Plant “Perception” and Plant “Appetite”
Following Albert, Siger(?) reports Isaac Israeli’s division of sensation (but ascribes it to Galen). Siger(?) accepts the claim that plants are able to distinguish between good and bad food, but, like Albert, he rejects the labeling of this capacity as a perceptual capacity, referring to the fact that if the so called natural sense is to be understood as a type of sense-perception, it would mean that we would also find pain and pleasure, desire, appetite and, ultimately, locomotion in plants.79 Siger(?) here anticipates the objection that there are stationary animals that have sensation but are still incapable of forward motion, and concludes that such animals are at least capable of moving, if not their whole body, a part of it, and if not by forward motion, by stretching towards something desirable and retracting from something harmful. Since plants lack both sensation and intellect, they cannot move by either of these and, therefore, they cannot move at all.80 It is not clear how Siger(?) explains the apparently similar motion in plants when these, for instance, grow towards the sunlight and away from harmful substances. Just as in Albert, this observation is not considered at all in the discussion.
Whereas the question above is not treated, Siger(?) addresses de An. 2.12, 424a32–b3 indirectly by adding the argument quod that plants can be destroyed by excessive stimuli and so must be able to sense.81 He refutes the argument by referring to Averroes’ theory of the variable nature of the sensible species as a corporeal being in the sensible object and as a spiritual one in the medium.82 When vultures sense the smell of a carcass fifty miles away, they do not perceive the sensible forms as the corporeal beings that they are in the sensible objects, but in the spiritual form they have in the medium.83 Siger(?)’s point seems to be that the sensible forms affecting the plant materialiter as corporeal beings is not the same as having sensation, that is, the capacity to also receive the sensible forms spiritualiter.84
The same argument and a similar, but not identical, refutation is found in Walter Burley85 and, in a fragmentary form, in Simon of Faversham, where the refutation apparently formed part of the quaestio’s solution; the only available manuscript starts off in the middle of it.86 The refutation in Burley and Faversham echoes Averroes’ explanation but does not include the distinction between material and spiritual transmission; the plant is said to be affected not by smell directly, but by bodies that carry it (“corpus habens odorem foetidum”) and by a “material condition” that is present in these bodies that “infects” the medium which, in turn, destroys the plant.
Whereas the other commentators from Albert onwards provide either no answer at all or quite fragmentary solutions to the question of how the plant feeds without perception and appetite, Peter of Auvergne puts quite an effort into providing a tenable explanation. In two separate quaestiones, Peter deals first with the question of whether plants have appetite and desire87 and, second, whether they have pleasure and pain.88 As to the former, Peter gives the following answer: since plants, like all living beings, need food to survive, and all living beings desire to survive, plants must also have an appetite and a desire for food. Appetite, according to Peter, falls into two main categories closely corresponding to Isaac’s division of sensation: natural appetite (appetitus naturalis) and animal appetite (a. animalis). The latter category falls into two subtypes: the intelligible and the sensitive. The former is called will (voluntas) and is found in the rational part of the soul. The latter falls into another set of subtypes: the concupiscible appetite (a. concupiscibilis), which is an attraction towards what appears desirable to the animal, and the irascible (a. irascibilis), which is a resistance towards what appears undesirable. The appetitus animalis and its subtypes, Peter concludes, require cognition; plants have only the appetitus naturalis – “an inclination towards something by a natural instinct and without cognition,”89 by which they are stimulated “to exist, to be preserved, and towards appropriate food.”90 The division is found already in Albert, who ascribes it to Averroes,91 but Peter’s systematic account of the division in response to the argument quod non in this case has no counterpart in the other commentaries here studied.
John of Jandun’s question commentary adds a couple of new elements to the discussion. Neither Albert nor any of the other commentators here studied problematise the fact that the plant’s ability to grow towards favourable conditions and retract from harmful ones could be seen as a type of voluntary motion analogous to that of stationary animals.92 Jandun is the only commentator on Somn.Vig. here studied to grant that the plant’s growth could be claimed to be a form of motion, but he dismisses the possibility that it can be claimed to be governed by appetite:
But plants do not move by themselves locally, because they do not move by themselves by stretching out and retracting or by forward movement, which is obvious. Nevertheless, it is true that they in some way and accidentally move locally by themselves in the respect that in some way locomotion accompanies movement of growth. But the reason that plants have this property is not that they have some power to pursue something insofar as it is appropriate, viz. the pursuit that accompanies appetite and processive motion in order to pursue [sc. the appropriate] or avoid [sc. the inappropriate].93
4 Conclusion
Aristotle’s classification of plants as ensouled beings without sense-perception and his subsequent conclusion that plants are incapable of sleep and waking raise and leave open a number of questions related to sense-perception that the medieval commentators on Somn.Vig. tried to answer. Their efforts center around three main problems. Two of these are intimately connected to the survival of the animate organism.
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(1) Perceptual capacity is necessary for the animal’s survival, and so is sleep, because the sensitive soul cannot function without intervals of inactivity. The nutritive soul, on the other hand – or at least the power by which the plant nourishes itself – has to operate continuously; when it reaches the limit of its capacity, the organism runs out of fuel and dies. The medievals provide a set of explanations for why the sensitive soul needs rest whereas the nutritive does not, and they employ a double strategy when doing so: they adduce a range of reasons why the nutritive process consumes very little of the organism’s spiritus, and the overall gist of their arguments seems to be that so little fuel is lost in process that the nutritive soul conducts its nourishing activity as a more or less self-sustaining system. At the same time, a corresponding set of arguments is adduced to explain why the sensitive soul cannot operate continuously. The standard explanation of the difference between the nutritive and sensitive soul in this respect is partly a matter of concentration of the spiritus and complexity of the organism, partly of motion and resistance: not only is it the case that in the animal organism, unlike in the plant, the various bodily organs, including the sensory organs when operating, must all be supplied with the spiritus; it is also the case that the animal’s forward motion, unlike the motion of the flow of the nutriment, wearies the body, because it is contrary to the nature of the animal’s body.
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(2) According to Aristotle, the plant is a self-nourishing being with no perception and hence neither touch nor taste. Thus, plants have no capacity to distinguish between appropriate and inappropriate food. Consequently, they are also incapable of locomotion, but so are some animals. So if the stationary animal’s stretching out towards favourable conditions and pulling back from conditions and substances that would otherwise harm it is the work of the animal’s sensitive soul and of desire, why could the apparently similar behaviour in the plant not also be claimed to be evidence of desire and appetite? If the capacity to distinguish good food from bad is vital to the stationary animal, why would it not be vital to the plant? The few of the Latin commentaries here studied that address the problem make some attempts at assuming a lower form of appetite in plants, which, contrary to animal appetite, is separate from perceptual capacity and still has the function of directing the plant towards appropriate food. Aristotle is very clear in de An.: plants do not have the “mean” that makes it possible for the animal to discern sensible qualities and differences between these.94 So, if not by perception as this mean, how is the appropriate target of this goal-directed motion of the plant identified by the nutritive soul? The accounts of the theory of natural vs. animal appetite in the commentaries on Somn.Vig. are terse and appear to generate more questions than they answer. It is perhaps somewhat telling that Peter of Auvergne, whose commentary on Somn.Vig. contains the most elaborate account of the theory, argues in his question commentary on Sens. that the reason that plants (as well as inanimate objects) have not been endowed with perception as protection against threats is that “nature cares more about the survival of the animal than that of plants and inanimate objects.”95
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(3) As to the question of how plants can lack the ability to perceive and still be acted upon by sensible objects, the commentators found an explicit answer in Aristotle’s claim that the form of a sensible object can act upon the plant but only together with the matter. Considering the complexity of the question and the lemma’s key role in it, the commentators devote surprisingly little attention to explaining the precise meaning of Aristotle’s expression “along with the matter” (
μετὰ τῆς ὕλης ) in de An. 2.12, 424b3. To receive the form without the matter is impossible for a being without sense-perception, and the reverse is impossible for all beings, but by some affection by the matter of the sensible object together with its form, the matter of the plant can, evidently, still undergo some kind of change. The precise nature of this change is not clear in Aristotle and the interpretation of de An. 2.12, 424a32–b3 has been much discussed in modern scholarship. This chapter will not dwell on the details of the contemporary debate.96 What can be concluded here, however, is that the nine medieval commentaries here studied provide little more than a superficial rendering of this important passage, which is clearly an appendix to the crucial definition of aísthēsis (αἴσθησις ) in de An. 2.12, 424a17–24. As mentioned above, Albert’s commentary on de An. does not bring much to the table in this respect, but it may be worthwhile to search further in the Latin tradition on de An. Further study of the reception of de An. 2.12, 424a32–b3, as well as further inquiry into the nature of the appetitus naturalis, is, I think, likely to contribute not only to the investigation begun in this chapter, but also to our knowledge of the reception of Aristotle’s theory of perception more broadly.
Acknowledgements
I am grateful to the members of the research group and in particular to Sten Ebbesen, Pavel Gregoric, Mika Perälä, Juhana Toivanen, Jari Kaukua, and Thomas Johansen for commenting on a draft of this paper.
See, in particular, Aristotle, De Anima, ed. W. D. Ross (Oxford: Clarendon Press, 1961), 1.5, 411b27–30:
The work was probably by Nicolaus of Damascus (c.64–?). An edition of Alfred of Sareshel’s Latin translation is available in H. J. Drossaart Lulofs and E. L. J. Poortman, eds., Nicolaus Damascenus De plantis: Five Translations (Amsterdam: North-Holland, 1989), 464–561. Alfred also wrote a commentary on De plantis, an edition of which is available in R. James Long, “Alfred of Sareshel’s Commentary on the Pseudo-Aristotelian De plantis: A Critical Edition,” Mediaeval Studies 47 (1985): 125–67. On Alfred’s biography and works, see Olga Weijers et al., Le travail intellectuel à la Faculté des arts de Paris: Textes et maîtres (ca. 1200–1500), 9 vols. (Turnhout: Brepols, 1994–2012), 1:58–60.
See Ps.-Arist., De plantis, 517.2–521.31.
For the date of Adam’s commentary, see Charles Burnett, “The Introduction of Aristotle’s Natural Philosophy into Great Britain: A Preliminary Survey of the Manuscript Evidence,” in Aristotle in Britain during the Middle Ages, ed. J. Marenbon (Turnhout: Brepols, 1996), 40–41. For a biographical overview of Adam of Buckfield, see Olga Weijers et al., Le travail intellectuel, 9:24–30. Adam’s commentary on Somn.Vig. is edited in Thomas Aquinas, Doctoris angelici divi Thomae Aquinatis opera omnia 24, ed. S. E. Fretté (Paris: Vivès 1875), 293–310.
De homine is the second part of Albert’s Summa de creaturis, which is believed to have been finished 1242 or earlier; see Henryk Anzulewicz and Joachim R. Söder, Alberti Magni De homine (Münster: Aschendorff, 2008), xiv–xv. For a chronology of Albert’s works, see James Athanasius Weisheipl, “Albert’s Works on Natural Science (libri naturales) in Probable Chronological Order,” in Albertus Magnus and the Sciences: Commemorative Essays, ed. J. A. Weisheipl (Turnhout: Brepols, 1980), 565–77. For a bibliographical overview, see Weijers et al., Le travail intellectuel, 1:34–47.
Adam of Buckfield, Commentarium in De somno et vigilia, in Thomas Aquinas, Doctoris angelici divi Thomae Aquinatis opera omnia 24, ed. S. E. Fretté (Paris: Vivès 1875), lectiones 1, 2.
Albert the Great, De hom., 326.1–329.76.
Albert the Great, De hom., 326.39–45: “Et ratio fundatur super hoc quod cuiuscumque partis animae propria passio est somnus, illam immobilitat et impedit ab actu. Ergo si nutritivae particulae, quae est pars vegetabilis, propria passio esset somnus, tunc ipsam immobilitaret et impediret ab actu; sed hoc falsum est, quia virtutes illae intenduntur in somnis in actibus suis.”
Albert believes that the Compendium is by Al-Fārābī; see Silvia Donati, “Albert the Great as a Commentator of Aristotle’s De somno et vigilia: The Influence of the Arabic Tradition,” in The Parva naturalia in Greek, Arabic, and Latin Aristotelianism, ed. B. Bydén and F. Radovic (Cham: Springer 2018), 173.
Averroes, Compendia librorum Aristotelis qui Parva naturalia vocantur, ed. A. L. Shields (Cambridge, MA.: Medieval Academy of America, 1949), 77.33–78.43. Averroes continues by stating that what withdraws from the sense-organs is the sensus communis (see 78.43–79.50).
“Sensus huius auctoritatis est quod somnus probatur esse passio sensus ex hoc quod plantae non dormiunt, sed bruta et homines dormiunt, quae non communicant nisi in anima sensibili; et cum in somno non immobilitentur nisi sensus exteriores et non interiores, erit somnus passio sensuum exteriorum et non interiorum.” (Albert the Great, De hom., 326.62–65.)
Albert the Great, De hom., 326.68–327.11.
“Ad id quod obicitur quod somnus sit passio vegetabilis, dicendum quod verum quidem est quod omne agens finite agit secundum tempus determinatum, sed non omne agens finite potest excellere tempus. A Philosopho enim dicitur illud agens excellere tempus quod opus suum facit cum labore et poena; illud enim si excedat modum suae virtutis in continuando opus, lassabitur et indigebit quiete ne corrumpatur.” (Albert the Great, De hom., 328.20–27.) Cf. De hom., 46.50–54, 324.14–28. For the expression “cum labore et poena,” cf. Albert the Great, Super Dionysium De caelesti hierarchia, ed. P. Simon and W. Kübel (Münster: Aschendorff, 1993), 221.7–13: “Videtur enim, quod angelus moveat corpus assumptum cum labore et poena. Labor enim et poena moventis contingit ex hoc quod mobile non ex toto oboedit moventi; sed corpus assumptum non ex toto oboedit virtuti moventis angeli, quia non semper movet ad motum naturalem illi corpori, cum moveat in diversas partes; ergo movet cum labore et poena.”
Also, see Somn.Vig. 2, 455b13–22.
As pointed out by Aristotle; see Somn.Vig. 1, 454a29–32:
“Et illius causam tangit Avicenna in VI de naturalibus et Averroes in libro De essentia orbis dicens quod talia agentia agunt in organo, cuius motus naturalis secundum naturam materiae contrarius est motui agentis. Dico autem motum agentis, quo movet agens; et hoc est verum de organis processivi motus, quae secundum naturam gravia sunt et descendunt deorsum, cum virtus motiva non moveat deorsum, sed in omnem partem.” (Albert the Great, De hom., 328.27–35.) I have been unable to locate the passage in Avicenna’s Liber sextus that Albert has in mind, but the second reference is to Averroes, De substantia orbis: Critical Edition of the Hebrew Text with English Translation and Commentary, ed. A. Hyman (Cambridge, MA: The Medieval Academy of America / Jerusalem: Israel Academy of Sciences and Humanities, 1986), 76; see also Averroes, Long Commentary on De caelo, in Aristotelis Omnia quae extant opera et Averrois Cordubensis in ea opera omnes, qui ad haec usque tempora pervenere commentarii, 9 vols. (Venice: Comin da Trino di Monferrato, 1562–1574; repr. Frankfurt am Main: Minerva, 1962), 2:5, 96v: “Causa enim fatigationis in animalibus est, quia in eis est principium motus contrariorum motui animae, scilicet pars gravis quae est in eis. Hoc autem movet nos multum ad contrariam partem illi, qua intendimus moveri ex anima nostra, quapropter accidit nobis labor et fatigatio”; 98v: “somnum enim et quies in animalibus necessario sunt in eis propter laborem, labor autem non est, nisi quia in eis existit principium contrarium motui animae.”
Albert the Great, De hom., 328.35–39.
Note, for instance, de An. 2.4, 416b20–31.
“In operibus autem vegetabilis animae non sic est. Opera enim ipsius sunt alimento uti et augmentare et generare; et haec omnia fiunt unico instrumento quod est calor naturalis, et fiunt etiam actione calidi, et ideo actio instrumenti eadem est et non contraria cum actione virtutis moventis. Unde etiam non potest causari lassitudo sicut causatur in virtutibus sensibilibus et virtutibus motivis motu processivo, et idcirco illae potentiae non possunt excellere tempus suae virtutis et suae proportionis ad actum.” (Albert the Great, De hom., 328.39–48.)
“Sunt tamen quidam hoc aliter solventes dicendo quod virtutes sensibiles apprehendunt delectabile in sensibus, et ideo vi delectationis incitantur ad opus, ita quod continuantur in ipso ultra tempus suae possibilitatis; sed non est talis apprehensio obiecti in virtutibus animae vegetabilis, et idcirco illae non excedunt tempus suum. Sed prima solutio verior est, quia illa tangit causam lassitudinis et poenae.” (Albert the Great, De hom., 328.49–56.)
Albert’s commentary on the Parva naturalia was written after his exposition in De homine, probably around 1256. On the date, see J. A. Weisheipl, “Albert’s Works,” 570, and Donati, “Albert the Great as a Commentator,” 170–71. Donati is currently preparing a critical edition of Albert’s commentary on Somn.Vig. for the Cologne edition.
For the movement of the nutriment, which according to Albert is of the same nature as the traction of a magnetic object to the magnet, Albert refers to his commentary on the Physics (Physica libri 1–4, ed. P. Hoßfeld (Münster: Aschendorff, 1987), 523.60–70) and to his De nutrimento et nutribili, ed. S. Donati (Münster: Aschendorff, 2017), 7.30–39; but note also Albert the Great, De anima, ed. C. Stroick (Münster: Aschendorff, 1968), 86.79–87.16.
See Albert the Great, De somno et vigilia, ed. A. Borgnet (Paris: Vivès, 1891), 126b: “Talis enim motus non est [sentire,] nutrire, et augere, […] quod cibus movetur naturaliter ad membrum sicut ad suum locum, et ad suum speciem per quantitatem ejus fit augmentum, et per superfluum ejus generatio, et ideo tales motus non inducunt lassitudinem, sed perfectionem; propter quod ex illis non causatur somnus nec etiam vigilia.” (The square brackets are my own; ‘sentire’ should be deleted or the text perhaps emended into ‘nutrire, augere, et generare’ or something similar.) Food makes the ensouled being grow qua quantitative (de An. 2.4, 416b12–14) and semen is a residue of nutriment (GA 1.18, 724b24–725a4). Also, cf. Avicenna, Liber de anima seu Sextus de naturalibus, ed. S. Van Riet (Louvain: Éditions Orientalistes / Leiden: Brill, 1968–1972), 1:5, 81.29–82.39 (and note Fazlur Rahman, Avicenna’s Psychology (London: Oxford University Press, 1952), 25.22–33); Albert the Great, De hom., 117.19–23.
To prove that sleep is not necessary for the plant, Albert has to explain not only why the digestive process in the plant does not generate a need for rest, but also why it (unlike the animal’s digestion; see Somn.Vig. 3, 456a30–458a26) does not presuppose sleep; see, for instance, Albert the Great, Quaestiones super De animalibus, ed. E. Filthaut (Münster: Aschendorff, 1955), 144.84–145.9, where Albert claims that the plant feeds constantly and does not absorb more than it can digest, whereas the animal feeds at intervals and, hence, its digestion needs extra strength immediately after eating, which makes it necessary for other bodily powers to subside temporarily: “Et praeterea planta continue sumit nutrimentum nec plus sumit quam possit digerere, et ideo somnus non est ei necessarius. Sed animal semel sumit nutrimentum, et ideo indiget, quod virtus digestiva magus confortetur post assumptionem nutrimenti quam antea, quod non potest fieri, nisi aliae virtutes cessent; ideo etc.”
For the role of the spiritus vitalis in relation to the spiritus animalis in Albert, see Miguel de Asúa, “War and Peace: Medicine and Natural Philosophy in Albert the Great,” in A Companion to Albert the Great: Theology, Philosophy, and the Sciences, ed. I. M. Resnick (Leiden: Brill, 2013): 277–81.
“Hoc autem est proprium dormientium, quod corpora sunt minora dormientia, et sunt majora vigilantia” (Albert the Great, De somno, 126a–b.)
“Et quod corpora sint minora uno tempore quam alio, non est nisi propter frigus aeris circumstantis, et non propter somnum. Et ex eadem causa est clausio florum in nocte, et apertio quae est in die.” (Albert the Great, De somno, 127a.)
Albert the Great, De somno, 134a–b.
Albert the Great, De somno, 126a–27a.
Perception of time is the task of the common sense, which plants do not have; see Mem. 1, 450a9–12. For a discussion of perception of time with reference to the common sense, see Pavel Gregoric, Aristotle on the Common Sense (Clarendon Press: Oxford, 2007), 99–111.
Juv. 4, 469b6–5, 470a5; 6, 470a19–31.
As claimed by Aristotle in de An. 2.3, 414a32–b7, and 3.12, 434b18–22.
“Et hoc quidem dicit Isaac Israelita Philosophus in libro de Elementis, distinguens duplicem tactum et duplicem gustum: dixit enim hos duos sensus inesse quibusdam naturaliter solum, et quibusdam naturaliter et animaliter: naturaliter autem dicit his inesse quae capit alimentum secundum substantiam solum, naturaliter vero et animaliter his quae capiunt alimentum secundum substantiam, et insuper habent potentias apprehensivas sensibilium specierum alimenti: plantis igitur videbuntur inesse per hanc rationem isti duo sensus, et per consequens ita erit in eis somnus et vigilia.” (Albert the Great, De somno, 125b–26a.)
Isaac Israeli’s Arabic original of the “Book on the elements” has not survived. Gerard of Cremona’s Latin translation is available in Omnia opera Ysaac … (Lyon: Bartholomeus Trot, 1515). Albert’s reference is to De elementis 2, fol. X, col. a, ll. 24–col. b, l. 2 (e.g.: “Et sensus quidem naturalis est qui est proprius arboribus et plantis et quoniam ipsa sunt naturalia, propter hoc sentiunt sensu naturali. Quod si naturae et complexioni suae conveniens est ex nutrimento, et delectantur eo et recipiunt ipsum assidue. Si vero diversum sibi et refugiunt ab ipso eo quod diversum est a natura et complexione ipsorum et expellunt ipsum a se […] et vegetabili quidem inest sensus naturalis, quo sentit in nutrimento et augmento suo, et animali inest cum sensu naturali sensus animalis quo sentit dolorem corporeum et mouet voluntarie”). For the debate against Isaac on this matter, see also Albert the Great, De an., 50.38–54; De caelo et mundo, ed. P. Hoßfeld (Münster: Aschendorff, 1971), 110.45–58; Super IV sententiarum, dist. XXIII–L, ed. A. Borgnet (Paris: Vivès, 1894), 511b; De vegetabilibus, ed. A. Borgnet (Paris: Vivès, 1891), 9a.
See Albert the Great, De somno, 126b: “[…] sensibilis enim particula gustus et tactus non diffinitur ab eo quod est capere alimentum tantum, sed ab eo quod est sensibiles species apprehendere sine materia.”
See de An. 3.13, 435a21–b1:
See Albert the Great, De an., 150.5–21: “Ulterius autem ex dictis manifestum est, quare plantae non habent sensum; licet enim patiantur a tangibilibus, quae agunt in ipsas actione materiae et non tantum actione speciei, et licet habeant quandam partem animae, tamen quia organa plantarum non sunt harmonice proportionata ad solas sensibilium species recipiendas, non possunt sentire plantae; carent autem huiusmodi harmonia in organis propterea, quia terrestres sunt, et ideo actiones earum ab actionibus materialibus elevari non possunt, sed patiuntur passione materiali, non formali, sicut diximus. Et ideo dicentes plantas habere duos sensus, gustum scilicet et tactum, absque dubio errant, quia licet trahant nutrimentum et alterentur tangibilibus, tamen non iudicant sapores nec alterantur alteratione speciei tantum, sed alteratione materiae. Hoc est igitur, quod convenit omni sensui, inquantum est sensus.”
See de An., 3.2, 426b8–12 on the sense-organs’ capacity to perceive differences in the sensible objects.
Albert the Great, De veg., 17a–18b. Albert’s commentary on De plantis probably dates to 1256–1257; see Gilla Wöllmer, “Albert the Great and his Botany,” in A Companion to Albert the Great, ed. Resnick, 226.
It may be mentioned that Peter of Auvergne’s Quodlibet, qu. 14 (edited by J. Koch in “Sind die Pygmäen Menschen: Ein Kapitel aus der philosophischen Anthropologie der mittelalterlichen Scholastik,” Archiv für Geschichte der Philosophie 40:2 (1931): 194–213) contains a similar line of argumentation in a very different context. The topic of Peter’s qu. 14 is whether pygmies are human beings. In addition to the observation that pygmies look like humans, Peter adduces as arguments quod sic various actions of the pygmies that appear to give evidence that they are rational beings, among these the fact that they seem to worship the sun: “Secundo quia sole oriente in regione illa moventur applaudantes eidem et quasi reverentiam exhibentes adorando ipsum, quod ad cultum religionis videtur pertinere, qui non est sine ratione, per quam distinguitur homo a non-homine” (Peter of Auvergne, Quodlibet, 210). Peter objects that this behaviour is not an indication of rational capacity but merely the result of the spiritus’ reaction to the warmth of the sun. He compares the phenomenon of the plant’s reaction to changes in temperature: “[…] oriente sole in illa regione virtute solis calefiunt corpora eorum et dilatantur spiritus, quod sentientes delectati moventur […]. Etiam videmus in plantis, quod sole ascendente ad cenith calefacte aperiuntur flores, sicut patet in solsequio, et descendente clauduntur constricte.” (Peter of Auvergne, Quodlibet, 213.) Peter is, however, quite clear about the fact that the pygmies actually perceive the heat: “[…] non est opus rationis intellectualis, sed eius que ad sensum pertinent que aliquam similitudinem ad rationem particularem habet in homine” (ibid.). I am grateful to Juhana Toivanen for calling my attention to Peter’s account.
“Animaliter autem inesse dicunt sensum, quando inest secundum solum animae actum vel passionem: et hoc est judicium sensibilium et apprehensio quam sola facit anima quando recipit formam sigilli immaterialiter omnino, sicut cera recipit figuram sigilli, nihil omnino recipiens de auro vel sigilli materia. Naturaliter autem inesse sensus dixerunt quando sensibilia insunt per actiones qualitatum materiae et per esse materiale quod habent in materia extra, sicut calidum inest calefacto, et dulce ei quod infunditur dulci substantia: et sic de aliis: quia per talem naturam agentis et patientis constituitur sensibile inesse materiali et naturali.” (Albert the Great, De veg., 17b.)
“Haec igitur est causa, quod hos sensus naturaliter acceptos plantis attribuerunt, non autem rebus inanimatis: quia in eis nulla est forma animae primo informans agentia, ut secundum ejus naturam corpus ipsum suscipiat sensibilium passiones, sed suscipiunt eas ut corpora tantum, ut diximus” (Albert the Great, De veg., 18a.)
“Similiter potest dubitari de eo quod dicit quod gustus est sensus alimenti. Si enim ita sit, cum plantae recipiant alimentum, videtur quod debeant habere sensum, ad minus gustum. Et dicendum quod gustus non dicitur sensus alimenti quia sit iudex super ipsum; solum enim iudicat de suo proprio obiecto, quod est sapor. Sed dicitur esse sensus alimenti secundum quod est receptivus alimenti. Non propter hoc oportet quod insit plantis, licet recipiant alimentum; illud enim quod in plantis recipit alimentum est natura quae non recipit nisi illud quod est conveniens rei. In animalibus autem non solum est natura recipiens alimentum, sed est ibi voluntas, quia recipitur cum voluntate. Et quia voluntas potest esse aliquando ad aliquid utile, aliquando ad nocivum, indiget animal in comprehendendo alimentum sensu quo discernat utile a nocivo, quamvis plantae non indigeant ista discretione, et ita nec sensu.” (Adam of Buckfield, De an., ad 3.12, 434b22; available in transcription of the MS Bologna, Bibl. Univ., 2344 (fol. 24r–53v) by J. Ottman:
In his question commentary on Aristotle’s works on animals (GA, HA, and PA, which all circulated under the collective title De animalibus in the medieval West), Albert grants that plants are able to accept suitable nutriment and reject that which is harmful, but he also denies that plants can distinguish the former from the latter by perception; see Albert the Great, Quaest. De animal., 129.44–130.8.
Ps.-Arist., De plantis, 517.3–5, 7–10.
The author of De plantis is as categorical as Aristotle: “Dico ergo quod plantae nec sensum habent nec desiderium: desiderium enim non est nisi ex sensu, et nostrae voluntatis finis ad sensum convertitur. Nec invenimus in eis sensum nec membrum sentiens nec similitudinem eius nec formam terminatam nec consecutionem rerum nec motum nec iter ad aliquid sensatum nec signum aliquod per quod iudicemus illas sensum habere, sicut signa per quae scimus eas nutriri et crescere.” (Ps.-Arist., De plantis, 518.11–12.)
See Albert the Great, De veg., 6a.
“Ad primam dicendum, quod in ossibus est actus primus ipsius sensus, quia vita diffunditur per omnes partes corporis et similiter sensus. Actus tamen secundus non est nisi in parte organica ipsius sensus. Ideo propter actum primum ipsius sensus et vitae est virtus discretiva convenientis et nocivi expulsiva, et tamen non est ibi sensus. Et propter [the edition reads praeter] hoc potest dici, quod in planta est virtus receptiva convenientis et nocivi expulsiva, et tamen non est ibi sensus.” (Albert the Great, Quaest. De animal., 129.76–130.8.) Cf. also Albert the Great, De veg., 4a–b, 274b.
See, for instance, de An. 2.5, 416b32–417a14.
De An. 3.12, 434b11–24.
Albert ascribes this argument to the proponents of the theory that plants do have sensation; see Albert the Great, De veg., 4a–b.
See Clemens Stroick, ed., Alberti Magni De anima (Münster: Aschendorff, 1968), v–vi.
See above, 194n39, and Albert the Great, De an., 150.14–15 (italics indicating quoted lemmata follow the Cologne edition): “[…] sed patiuntur passione materiali, non formali, sicut diximus.” Both James of Venice’s and William of Moerbeke’s translations render Aristotle’s
Averroes does not quote or comment on
For a bibliographical overview, see Weijers, Le travail intellectuel, 3:31–35. Note Silvia Donati, “Goffredo di Aspall (†1287) e alcuni commenti anonimi ai Libri naturales nei mss. London, Wellcome Hist. Med. Libr., 333 e Todi, BC, 23 (Qq. super I De gen. et corr., Qq. super Phys. V, VI) Parte I,” Documenti e studi sulla tradizione filosofica medievale 23 (2012): 245–320, and “… parte II,” Documenti e studi sulla tradizione filosofica medievale 24 (2013): 219–418. On Aspall’s question commentary on Somn.Vig., see Sten Ebbesen, Christina Thomsen Thörnqvist, and Véronique Decaix, “Questions on De sensu et sensato, De memoria and De somno et vigilia: A Catalogue,” Bulletin de Philosophie Médiévale 57 (2015): 96–98. Aspall’s commentary is edited in Sten Ebbesen, “Geoffrey of Aspall, Quaestiones super librum De somno et vigilia: An Edition,” Cahiers de l’Institut de Moyen-Âge Grec et Latin 83 (2014): 257–341.
MS Rome, Bibl. Angelica, 549, fol. 104vb–112rb (hereafter Anon. Angel., Quaest. Somn.Vig.). See Ebbesen, Thomsen Thörnqvist, and Decaix, “Questions,” 106–7. I am currently preparing a critical edition of the work.
The commentary is preserved in MSS Rome, Bibl. Angelica, 549, fol. 99vb–104va and Munich, BSB, Clm. 9559, fol. 47ra–51rb. The Rome manuscript contains only the first quaestio on Insomn., viz. the question whether dreaming is an affection of the common sense, whereas the Munich manuscript contains six additional questions on Insomn. and six on Div.Somn.; see Ebbesen, Thomsen Thörnqvist, and Decaix, “Questions,” 100–101. For an overview of all of Siger’s works, see Weijers and Calma, Le travail intellectuel, 9:55–89. On the attribution to Siger of Brabant, see Jan Pinborg, “Die Handschrift Roma Bibliotheca Angelica 549 und Boethius de Dacia,” Classica et Mediaevalia 28 (1969): 383. I am currently preparing a critical edition of the commentary.
Peter’s commentary is edited in Kevin White, Two Studies Related to St. Thomas Aquinas’ Commentary on Aristotle’s De sensu et sensato together with an Edition of Peter of Auvergne’s Quaestiones super Parva naturalia (PhD dissertation, Ottawa, 1986), 2:203–20. For an overview of Peter’s works, see Griet Galle, “A Comprehensive Bibliography on Peter of Auvergne, Master in Arts and Theology at Paris,” Bulletin de philosophie médiévale 42 (2000): 53–79; Weijers, Le travail intellectuel, 7:95–127. On the content of the quaestiones on Somn.Vig., see Ebbesen, Thomsen Thörnqvist, and Decaix, “Questions,” 102.
Bibliographical overview in Weijers and Calma, Le travail intellectuel, 9:99–111. On the content of the quaestiones on Somn.Vig., see Ebbesen, Thomsen Thörnqvist, and Decaix, “Questions,” 105. Simon’s commentary is edited in Sten Ebbesen, “Simon of Faversham, Quaestiones super librum De somno et vigilia: An Edition,” Cahiers de l’Institut de Moyen- Âge Grec et Latin 82 (2013): 90–145 (see pp. 93–94 for the date of Simon’s commentary on Somn.Vig.).
John of Jandun’s question commentary is still only available in four medieval manuscripts and some early prints. The text in Ioannis Gandavensis philosophi acutissimi Quaestiones super Parvis naturalibus, ed. A. Apulus (Venice: Hieronymus Scotus, 1557), 33rb–47ra, has been used throughout this chapter. Bibliographical overview: Weijers, Le travail intellectuel, 5:87–104. See Ebbesen, Thomsen Thörnqvist, and Decaix, “Questions,” 110–12, for a list of the quaestiones included.
Buridan’s question commentary on Somn.Vig. is here quoted from George Lockert’s edition: Quaestiones et decisiones physicales insignium virorum Alberti de Saxonia … Thimonis … Buridani in Aristotelis … Librum de Somno et Vigilia (Paris: Josse Bade, 1516), XLIIr–XLVIIv. A critical edition of the full question commentary on the Parva naturalia is supposed to be available in Jana Burydana, Quaestiones super Parva naturalia Aristotelis: Edycja krytycna i analiza historyczno-filozoficzna, ed. M. Stanek (Katowice, 2015), to which I have unfortunately had no access. For a bibliographical overview of Buridan’s works, see Weijers, Le travail intellectuel, 5:127–65; on the content of the quaestiones on Somn.Vig., see Ebbesen, Thomsen Thörnqvist, and Decaix, “Questions,” 112–13.
Bibliographical overview in Weijers, Le travail intellectuel, 6:37–62. Simon of Faversham’s and Walter Burley’s commentaries are closely related, but it is not clear whether the many similarities are due to a dependence on a common source or to one work being dependent on the other; see Christina Thomsen Thörnqvist, “Walter Burley’s Expositio on Aristotle’s Treatises on Sleep and Dreaming: An Edition,” Cahiers de l’Institut de Moyen-Âge Grec et Latin 83 (2014): 379–515.
I have used Quaestiones super libros Aristotelis, inc. 2: Quaestiones super parva naturalia Aristotelis (Cologne: Heinrich Quentell, 1489); see Weijers, Le travail intellectuel, 5:174; Ebbesen, Thomsen Thörnqvist, and Decaix, “Questions,” 115.
See Ebbesen, “Geoffrey of Aspall, Quaestiones,” 261.
See Geoffrey of Aspall, Quaest. Somn.Vig., 285: “Ad rationes ostendentes quod somnus et vigilia insunt substantiis separatis et etiam corporibus supralunaribus dicendum quod non quaecumque actualis operatio facit vigiliam, sed solum actualis operatio circa sensum. Unde, licet ibi sit actualis operatio circa intellectum sive actuale intelligere, non tamen est ibi vigilia proprie nisi extendendo nomen vigiliae.”
Geoffrey of Aspall, Quaest. Somn.Vig., 285. As a standard refutation, the commentators conclude that it is not just any circulation of the spiritus in the body that is sleep, but the process where the sensory apparatus is immobilised. Albert’s explanation of the alternating outward and inward flow of the spiritus in the plant merely as a reaction to air temperature and with no restoring function becomes commonplace in the later commentaries; cf. Peter of Auvergne, Quaest. Somn.Vig., 209.41–48; Simon of Faversham, Quaest. Somn.Vig., 100, 101; Anon. Angel., Quaest. Somn.Vig., fol. 105rb–va; Walter Burley, Exp. Somn.Vig., 414.2–7, 415.3–12, and 417.21–418.1. Also, cf. Albert the Great, Quaest. De animal., 144.44–53; John of Jandun, Quaest. Somn.Vig., fol. 36ra–b; John Buridan, Quaest. Somn.Vig., fol. XLIIva, XLIIvb.
Geoffrey of Aspall, Quaest. Somn.Vig., 285; cf. Siger of Brabant(?), Quaest. Somn.Vig., fol. 101va; Walter Burley, Exp. Somn.Vig., 418.24–419.2. Also, note the argument in Albert (Quaest. De animal., 144.84–145.9) that the fact that animals and plants feed in different ways contributes to the difference in need for rest: plants feed continuously whereas animals feed at intervals; hence, the need to fortify the digestion in the animal immediately upon the intake of food has no counterpart in the plant. (“Et praeterea planta continue sumit nutrimentum nec plus sumit quam possit digerere, et ideo somnus non est ei necessarius. Sed animal semel sumit nutrimentum, et ideo indiget, quod virtus digestiva magis confortetur post assumptionem nutrimenti quam antea, quod non potest fieri, nisi aliae virtutes cessent; ideo etc.”)
See Geoffrey of Aspall, Quaest. Somn.Vig., 284, 285; Siger of Brabant(?), Quaest. Somn.Vig., fol. 101va; Anon. Angel., Quaest. Somn.Vig., fol. 105va; Walter Burley, Exp. Somn.Vig., 413.15–414.1, 417.1–20; Peter of Auvergne, Quaest. Somn.Vig., 208.3–8, 209.33–45; John of Jandun, Quaest. Somn.Vig., fol. 35rb–va; John Buridan, Quaest. Somn.Vig., fol. XLIIva–b; John Versor, Quaest. Somn.Vig., fol. 246ra, 246va. Simon of Faversham’s commentary does not contain the argument in full: the beginning of the relevant quaestio is missing in the only text witness, the MS Oxford, Merton College Library, 292 (O.1.8), fol. 368ra. See Ebbesen, “Simon of Faversham, Quaestiones,” 100. Jandun and Buridan both indicate that the argument that also the nutritive soul must need to rest at some point is the most difficult to refute; see John of Jandun, Quaest. Somn.Vig., fol. 35rb: “Item difficilius, cuiuscumque rei naturalis est aliquod tempus determinatum secundum naturam, cum excesserit tempus, in quo natum est agere: oportet quod deficiat ab agendo”; John Buridan, Quaest. Somn.Vig., fol. XLIIvb: “Sed hic accidit magna dubitatio, quare virtus nutritiva non fatigatur in operando nec indiget requie ut virtus sensitiva.”
“Virtutes enim sensitiuae non semper reperiuntur in sua ultima perfectione, sed uirtutes uegetatiuae semper in sua ultima perfectione reperiuntur. Ex hoc contingit, quod uirtutes [quod] non necesse est (quod del. ms) in plantis deficere in operationibus, ut in uegetando, quia uirtus uegetatiua semper agit et est operans in eo, cuius est, usque ad ultimam perfectionem siue ad ultimum (ultimam ms) suae perfectionis, et non est ⟨sic⟩ de uirtute sensitiua in animali” (Siger of Brabant(?), Quaest. Somn.Vig., fol. 101va); cf. Peter of Auvergne, Quaest. Somn.Vig., 209.32–41; Simon of Faversham, Quaest. Somn.Vig., 101; Walter Burley, Exp. Somn.Vig., 417.1–4.
“Item continue agit propter saluationem animalis, quod mixtum est ex contrariis, et ex actione continua contrariorum fit deperditio continua, et ideo requiritur aliquae uirtus, quae continue restauret continuam deperditionem. Sed ad saluationem animalis non est necesse semper sentire; ideo et cetera” (Siger of Brabant(?), Quaest. Somn.Vig., fol. 101va); cf. John of Jandun, Quaest. Somn.Vig., fol. 35va. Also, cf. Albert’s account of the function of the virtus animalis vs. that of the virtus naturalis and vitalis in Albert the Great, Quaest. De animal., 144.68–79. On the body as composed of contraries, see de An. 1.4, 407b27–32. Cf. Albert the Great, De gen., 146.21–28.
This becomes a standard explanation in the commentaries after Albert; see, for instance, Anon. Angel., Quaest. Somn.Vig., fol. 105va; Simon of Faversham, Quaest. Somn.Vig., 100; John Versor, Quaest. Somn.Vig., fol. 246va.
“Omnia possunt deficere in actu sentiendi, et huius est causa, quia uirtus uegetatiua est solum uirtus actiua; gustare et tangere quaedam actiones sunt, uirtutes autem passiuae sunt sensitiuae. Cuius operatio consistit in quodam pati magis indiget recreatione et quiete quam cuius operatio consistit in agere” (Siger of Brabant(?), Quaest. Somn.Vig., fol. 101va); cf. Walter Burley, Exp. Somn.Vig., 418.2–8. That the patient is in more need of recovery than the agent seems a somewhat surprising claim but it probably has its origin in the doctrine that the action is in the patient, which goes back to Ph. 3.3, but note also de An. 2.2, 414a11–12:
Simon of Faversham, Quaest. Somn.Vig., 101.
See also Walter Burley, Exp. Somn.Vig., 418.12–23; John of Jandun, Quaest. Somn.Vig., fol. 35va. Jandun suggests that the spiritus recovers while operating: “Et ideo diversitas huius forte est ista, quia ipsa planta in opere nutritionis suae non consumit magnam multitudinem spirituum, quia spiritus eius sunt grossiores et durabiliores et ideo non est necesse, quod quandoque planta quiescat a nutriendo per aliquod tempus, ut huiusmodi spiritus restaurentur, sed in operando sufficienter restaurantur. Sed ipsum animal in sentiendo multos spiritus consumit aut debilitatur propter subtilitatem et passibilitatem ipsorum spirituum.” In Buridan, it is rather the fact that the spiritus flows from the inner parts of the body to the external senses that makes the perceiving animal consume it faster: “Sed in opere sensuum exteriorum natura indiget mittere spiritus ad organa exteriora ad exercendum opera sua et illi spiritus iam in organis exterioribus existentes cito propter subtilitatem exhalant” (John Buridan, Quaest. Somn.Vig., fol. XLIIvb).
“Sed illud non placet aliquibus, quia certum est, quod in operatione nutritionis oportet fieri aliquam consumptionem spirituum. Et adhuc nutrimentum de natura sua habet deorsum, sed in nutritione movetur ad omnem differentiam positionis. Propter quod videtur moveri contra suam naturalem inclinationem, et sic videtur, quod indiget quiete, ut in operatione sufficienter restituatur spiritus.” (John of Jandun, Quaest. Somn.Vig., fol. 35vb.)
See, e.g., de An. 2.2, 413b22–24; cf. Walter Burley, Exp. Somn.Vig., 415.20–416.4; John of Jandun, Quaest. Somn.Vig., fol. 35rb. Burley and Jandun refute Isaac’s theory on identical grounds: plants do not have sensation because they are too earthy; hence, they are unable to receive the form without the matter.
“Intelligendum, sicut narrat Albertus supra librum De somno et uigilia, quod Galenus dixit triplicem sensum: unum naturalem, qui est in plantis, quo attrahunt conueniens nutrimentum et refutant disconueniens, quod est eis contrarium. Secundum animalem, qui est in brutis, tertium intellectualem, qui est in hominibus. Sic autem dicere non est, nisi aequiuocare uocabulum sensus; si enim uirtutem existentem in plantis uocemus sensum, et similiter alias. Hoc est autem aequiuoce, sed de sensu proprie dicto est quaestio, et uidetur, quod plantis non inest sensus hoc modo. Et ratio Aristotelis ad hoc est, quod tunc in eis esset appetitiua particula, et per consequens delectio et tristitia; illud autem totaliter, quod quaeritur, probat et non est petitio, quia, cum alicui inest appetitus, eis inest motus secundum locum, de quo ad locum aut saltim motu delectationis et contristationis. Haec autem non mouent plantas, quia duo sunt principia motiua animalis: Aut enim mouetur appetitu intellectuali aut appetitu sensuali ita, quod idem inest appetitus. Si tamen obicias: ‘Terrae affixa habent appetitum et tamen non mouentur,’ dico, quod si huiusmodi animalia non mouentur secundum totum, mouentur tamen ⟨motu⟩ dilatationis et constrictionis. Et secundum partem mouentur, quia secundum quod sentiunt aliquod dilectabile, dilatantur et mouentur secundum partem. Secundum autem quod aliquid nociuum, constringuuntur. Et huiusmodi appetitus non est in plantis.” (Siger of Brabant(?), Quaest. Somn.Vig., fol. 101va.) Cf. Walter Burley, Exp. Somn.Vig., 413.9–14, 414.8–17, and 416.20–23.
Siger(?) refers to De plantis for the observation that plants can be destroyed by excessive sensible qualities such as strong odours (Siger of Brabant(?), Quaest. Somn.Vig., fol. 101va), but I have been unable to find the passage there.
Averroes, Comm. magnum in De an. 2, 276.7–278.77 (for the example of the vultures, see ibid., 2, 278.49–50). On this passage and interpretations of it in other thirteenth-century commentators on Aristotle’s theories of sense-perception, see Simo Knuuttila and Pekka Kärkkäinen, “Medieval Theories,” in Sourcebook for the History of the Philosophy of Mind: Philosophical Psychology from Plato to Kant, ed. S. Knuuttila and J. Sihvola (Dordrecht: Springer, 2014), 68–70.
“Ad primam rationem in oppositum, quod secundum Commentatorem secundo De anima quaedam sunt, quae multiplicant se spiritualiter, ut albedo et odor, et quaedam sensibilia sunt, quae multiplicant materialiter (sensualiter ms). Quod odor multiplicatur spiritualiter, quia quae spiritualiter se multiplicant per magnam distantiam multiplicantur, hoc ostendit per hoc, quod uultures per quinquaginta miliaria ueniunt ad cadauera mortuorum. Sed non posset esse tanta multiplicatio odoris materialiter; quare spiritualiter ibi solum multiplicabatur. Dico ergo, quod illud, quod transmutatur a sensibili spiritualiter sensum habet, non autem quando materialiter. Et uerum est, quod uniuersaliter sensibilia immutant sensus suos spiritualiter; unde odor sensum olfactus et color uisum. Unde dico, quod, si immutetur spiritualiter ⟨***⟩ sed si corrumpatur ab aliquo excellenti sensibili materiali, non est necesse.” (Siger of Brabant(?), Quaest. Somn.Vig., fol. 101va.) Cf. Thomas Aquinas, Sententia De anima, ed. R.-A. Gauthier (Rome: Commisio Leonina / Paris: Vrin, 1984), 2, 20, 152–53; John Buridan(?), Quaestiones super librum De anima, ed. B. Patar in Le traité de l’âme de Jean Buridan (de prima lectura) (Louvain-la-Neuve: Editions de l’Institut supérieur de philosophie, 1991), qu. 22 (“Utrum odor sit in medio realiter an spiritualiter”), 621.1–624.25 (= Lockert XVIIIra–XLVIIva). Patar attributes the commentary to Buridan, but its authenticity has been questioned; see Sander W. de Boer and Paul J. J. M. Bakker, “Is John Buridan the Author of the Anonymous Traité de l’âme Edited by Benoît Patar?” Bulletin de Philosophie Médiévale 53 (2011): 283–332. Also, note Albert the Great, De an., 135.12–51 on de An. 2.9, 421b10–13.
Cf. Averroes, Comm. magnum in De an. 2, 318.6–11.
See Walter Burley, Exp. Somn.Vig., 415.13–18; 419.4–9. Siger(?) refers to De plantis for the observation that plants can be destroyed by excessive sensible qualities such as strong odours, but I have been unable to find the passage there. Burley erroneously ascribes it to Theophrastus’ “On Plants” (Walter Burley, Exp. Somn.Vig., 415.16–17).
Simon of Faversham, Quaest. Somn.Vig., 100.
Peter of Auvergne, Quaest. Somn.Vig., 210.3–211.32.
Peter of Auvergne, Quaest. Somn.Vig., 211.33–212.22.
Cf. Thomas Aquinas, Summa Theologiae (Rome: Commissio Leonina, 1897), 1.78.3; see Robert Pasnau, Thomas Aquinas on Human Nature: A Philosophical Study of Summa Theologiae, 1a 75–89 (Cambridge: Cambridge University Press, 2001), 209–12.
Peter of Auvergne, Quaest. Somn.Vig., 211.27–31: “Appetitus naturalis est inclinatio ad aliquid instinctu naturae et non ex cognitione; appetitus animalis est inclinatio ad aliquid cum cognitione.” Note that in Albert’s account of Isaac’s theory in De veg., 17a, the division of sensation is explicitly linked to a corresponding division of desire, and the difference between the two main types is based on the absence vs. presence of cognition as in the division into natural and animal appetite in Peter: “Quod enim Plato desiderium inesse dixit plantis et appetitum, et alii quidam sensum, planum est intelligere si quis inspiciat rationes eorum. Ipsi enim, sicut testatur Isaac, duplex dixere desiderium et duplicem sensum. Unum quidem, quod est cum apprehensione desiderati et sensibilis et aliud quod est sine apprehensione omni. Et ideo, quando sensum attribuerunt plantae, non dederunt [desiderunt Borgnet] ei sensum et desiderium cum apprehensione sensibilis et desiderati, sed sine his.” In the brief quaestio on whether plants have pleasure and pain Peter concludes without much further ado that since plants do not have cognition, they are affected by neither of these.
Albert the Great, Phys., 73.78–81. It is not clear to me which passage Albert is referring to, but see Averroes, Comm. magnum in De an. 3, 522.22–28 on de An. 3.10, 433b7–8.
Aristotle mentions in de An. 2.2, 413a25–b1 the plant’s ability to grow in all directions:
“Plantae autem non moventur secundum locum per se, non enim moventur ex se motu dilatationis et constrictionis, neque processivo motu, ut manifestum est. Verum tamen est, quod aliquo modo moventur localiter ex se per accidens in quantum motum augmenti consequitur aliqualiter motus localis, sed hoc non est eis per se quia habeant aliquam virtutem apprehendentem aliquid sub ratione convenientis, quam apprehensionem consequatur appetitus et motus secundum locum ad prosequendum vel fugiendum.” (John of Jandun, Quaest. Somn.Vig., fol. 35rb.)
Cf. de An. 2.12, 424a32–b3 with 2.11, 424a2–10.
“Similiter dico sensus gustus est necessarius animali quia animal est vivum et nutribile; ei autem secundum quod vivum et nutribile competit cibus conveniens, et contrarium huius corrumpit ipsum vivum. Et ideo animali datus est sensus gustus ut cognoscat quis cibus sit conveniens et quis non conveniens. Unde natura, magis intendens salutem animalium quam plantarum vel inanimatorum, dedit animalibus, quae sunt in gradu superiori, tactum et gustum, et non plantis vel inanimatis.” (Peter of Auvergne, Quaest. Sens., qu. 10, 23.28–36.)
Note, in particular, Richard Sorabji, “Intentionality and Physiological Processes: Aristotle’s Theory of Sense-Perception,” in Essays on Aristotle’s De anima, ed. M. Nussbaum and A. Oksenberg Rorty (Oxford: Clarendon Press, 1995), 215–18, and the concise and helpful overview of the debate in Ronald Polansky, Aristotle’s De anima (New York: Cambridge University Press, 2007), 353n27. I quote here, with Polansky, David Bradshaw, “Aristotle on Perception: The Dual-Logos Theory,” Apeiron 30 (1997): 148: “It is well known that the closing statement, that plants are affected ‘together with matter,’ is ambiguous. Does it refer to the matter of the plants, the point being that plants are affected in their matter as a substrate? Or does it refer to the matter of the objects affecting them, the point being that plants undergo change by incorporating matter?” See also Damian Murphy, “Aristotle on Why Plants Cannot Perceive,” Oxford Studies in Ancient Philosophy 29 (2005): 295–339.