1 Introduction
The reception of Aristotle’s De insomniis in the Latin West centered around the mechanisms of dream formation. There are several reasons for this. Aristotle’s account of the process contains many ambiguities and unclarities and leaves important questions unanswered. Furthermore, the question of how and where in the body dreams are formed was intimately connected with the interpretation of Aristotle’s definition of dream, enýpnion.1 This chapter will demonstrate how the medieval commentators’ struggle with the Aristotelian text and, in particular, with reconciling Aristotle’s theory of dream formation with other parts of his psychology resulted in a rather unified explanation of dream formation that included several deviations from Aristotle. Its aim is to demonstrate the most central interpretative problems and the major general tendencies in the proposed solutions to these problems in a selection of commentaries on the Parva naturalia dated to the thirteenth and fourteenth centuries. The following works have been consulted: Albert the Great’s (1206/7–1280) exposition of De insomniis in his De homine and his commentary on the Parva naturalia,2 the question commentaries on Somn.Vig. by Geoffrey of Aspall (d. 1287), James of Douai (fl. c.1270), Radulphus Brito (d. 1320/21), John of Jandun (1280/89–1328), Simon of Faversham (d. 1306), and John Buridan (before 1300–1361), two question commentaries in the MS Rome, Biblioteca Angelica 549 (one anonymous (1270–1300?) and one ascribed to Siger of Brabant (c.1240–1281/82)), and the expositio on Somn.Vig. by Walter Burley (c.1275–after 1344).3
2 Aristotle
Aristotle’s theory of dreaming as put forth in De insomniis can be understood only against the background of his definition of sleep in De somno et vigilia as an immobilisation that affects not only the five particular senses, but also “the sense-organ which is master of all the rest,” which is also the organ of the common sense, by which we are aware that we perceive the external world.4 Aristotle has previously5 defined sleep as an “immobilisation of the senses” and also stated that no living being can have any sensation in sleep.6 Hence, when “the master sense-organ” is affected by sleep, it is immobilised and all the particular senses are immobilised with it:
For when the sense-organ that controls all the others, and upon which the others converge, has undergone some affection, then all the rest must be affected with it; whereas if any one of the latter is disabled, the former need not to be disabled as well.7
In other words, even if we were to lose one or several of our external senses, as long as we were awake, the common sense would still be able to inform us that we were not perceiving by the senses that we had lost. With this in mind, let us proceed to an overview of the process of dream formation as described by Aristotle in De insomniis.
In Insomn. 2, 459a23ff., Aristotle describes the first stage of the process by which dreams are formed: When we are awake and we perceive a sensible object in the outside world, the sensible object will produce sensation in our corresponding sense-organ. This affection will also remain in the organ after the sensible object is no longer present. A necessary condition for this persisting affection of the sense-organs has been defined already in De anima:
[…] for each sense-organ is able to receive the perceptible object without the matter. That is why, even when the perceptible objects have gone away, sensations, and imaginings are present in the sense-organs.8
The persisting movements, kinḗseis (
The examples of continuous perception mentioned are all temporary phenomena; chain-reactions in air and liquid are described as a motion that “continues to be produced […] until a standstill is reached.”10 It is, however, not clear from Aristotle’s account whether the movements of the remnants of external sense-impressions in the sense-organs eventually reach such a standstill, nor is it clear whether they are (or can be) recirculated in the body. Surely, it must have been a well-known phenomenon to Aristotle that dreams can recur, but there is no mention of this phenomenon. The formation of dreams is described by Aristotle as a one-way process: The movements generated by the persisting sense-impressions are stored in the sense-organs until they gradually start moving inward in the body.
In Insomn. 3, 460b28ff., Aristotle describes the next stage of dream formation as follows: when we fall sleep, the senses are deactivated and can no longer receive external stimuli. But the sense-impressions that were stored in our sense-organs when we were awake now become detectable. The reason for this is that when we are awake and the external senses are active, the remnants of earlier sense-impressions go unnoticed, because they are weaker and hence more difficult to detect than the stronger external stimuli that we perceive when we are awake. However, when we fall asleep, the flow of the bodily heat is reversed from outwards to inwards and the movements travel with the flow to the “starting-point [archḗ] of perception,” that is, the heart, “and become apparent.”11
Aristotle holds that the quality of the phántasma, that is, the degree of its resemblance to the external sense-impression that generated it, depends on the quantity of the heat and the speed with which it moves: Sometimes no phántasma at all appears, and sometimes it appears in a severely distorted form.12 Sometimes, however, the phántasma is so clear that its sharpness, together with a certain awareness that the movements originate from the sense-organs, makes the sleeper believe that he is perceiving not a phántasma that is a resemblance of a real object but the real object itself:
When in sanguineous animals the blood has subsided and its purer elements have separated off, the movement of sense-impressions persisting from each of the sense-organs makes the dreams coherent. Thus something is made to appear, and because of effects carried inward from vision one judges that one is seeing, or because of those from hearing, that one is hearing; and so on similarly for those from the other senses. For even when one is awake, it is because the movement from those sources reaches the starting-point that one judges that one is seeing, hearing, or perceiving. […] For in general the starting-point affirms the report from each sense, provided that some other, more authoritative one does not contradict it. In every case, then, something appears, yet what appears is not in every case judged to be real; it is, though, if the critical part is held in check or fails to move with its own proper movement.13
Aristotle’s description of the process of the formation and “perception” of dreams leaves many questions unanswered. To start with, it is not clear precisely how and to what degree the movements are stored in the sense-organs. Aristotle says explicitly that the páthos (
Just so, the movements are there potentially, but become activated as soon as what impedes them is removed. Upon being released, they move in the little blood remaining in the sense-organs, while taking on a resemblance, as cloud-formations do, which people liken now to men and now to centaurs as they change rapidly.18
But where in the body are the movements actualised? On the one hand, Aristotle says that when we fall asleep and the blood retracts inwards, the movements travel with it, and some of them are then actualised in the blood.19 But he also seems to claim that it is in the sense-organs when the blood retracts that the movements are actualised.20 Furthermore, the nature or mechanisms of the “perception” of these more or less distorted remnants of sense-impressions at their final destination is not discussed, nor is it clear from the account in De insomniis how phantásmata are generated from these remnants. Instead, the remaining account focuses on how we are often deceived by our dreams because in sleep we are unaware that we are dreaming and instead believe that we are actually perceiving. The account of our “perception” of the phantásmata is confined to mentioning (1) how “the starting-point affirms the report from each sense, provided that some other, more authoritative one does not contradict it,”21 and, at the same time, (2) “one’s ruling and judging part”22 in sleep often, but not always, accepts movements from the remnants of authentic sense-impressions as if we were still perceiving.23 After some examples of authentic sense-impressions in sleep (that are non-authentic dreams and not phantásmata), the account finally ends in Aristotle’s formal definition of the dream:
Rather, it is an appearance (phantasma) that arises from the movement of the sense-impressions, while one is in the sleeping state and in virtue of one’s being asleep, that is the dream proper.24
To sum up, Aristotle leaves us with at least the following questions: How is it possible for the sense-organs to store external sense-impressions? If these sense-impressions can remain in the sense-organs potentially, where in the body are they actualised? At what point in the process do we “perceive” these remnants of sense-impressions as dreams? Under which circumstances are we deceived by our dreams in the sense that we interpret them as external sense-impressions of the present? And under which circumstances are we aware already in our sleep that they are just dreams?
3 Albertus Magnus
There is evidence that the literal commentary on Aristotle’s treatises on sleep and dreams by Adam of Buckfield (c.1220–before 1294) circulated before the commentaries by Albert the Great appeared,25 but, as previously mentioned,26 there is no indication that Albert used Adam’s work. Be that as it may, there can be no doubt that Albert’s commentaries more than any other work of the time laid the foundations of the Latin reception of the Parva naturalia, and the Latin tradition on Aristotle’s theories on sleep and dreams is no exception.
Albert devotes the first questions in his exposition of De insomniis in De homine to the topic of Insomn. 1: the question of whether dreaming is an affection of the intellect, of opinion, or of perception. Albert’s major argument in support of Aristotle’s conclusion that dreaming belongs to the sensitive faculty in its imagining capacity27 is a reference to the mechanisms of dream formation as described in Averroes’ (which Albert, when writing the Summa, believes is al-Fārābī’s28) Compendium on the Parva naturalia: When we are awake, the movements caused by the sensible species move from the senses to imagination, but when we dream, they move in the opposite direction.29 Albert relies on the following passage in Averroes:
While awake, the external sensibles move the sense, and the common sense moves the imaginative power. While asleep, when the imaginative power imagines the intention which it has received from outside or from the recollecting power, it returns and moves the common sense and the common sense moves a single sense. So it happens that a human being perceives sensibles, although they are not external, since their intentions are in the organs of the senses regardless of whether they come from outside or from inside.30
The course of the movements here described is adopted by Albert with some modification, to which we will return in the following. As we shall see, Averroes’ model and Albert’s adaption of it fill in some of the blank spots in Aristotle’s account but, at the same time, generate new questions.
Albert finds Aristotle’s claim that stimuli are stored in the sense-organs difficult to accept and devotes a separate chapter to this discussion.31 Averroes’ claim that imagination is the starting-point of the movement of the sensible species in sleep is one of Albert’s counterarguments,32 together with the observation (attributed by Albert to Avicenna) that if the sensibilia were stored in the sense-organs, the blind would not be able to see colours in their dreams.33 In opposition to Aristotle, Albert follows Avicenna’s localisation of both imagination and the common sense34 in the brain and concludes that the sensible species are not stored in the sense-organs, but in imagination and, hence, in the brain.35 To reconcile this conclusion with Aristotle’s explicit claim that the sensible species are stored in the sense-organs, Albert interpolates Insomn. 2, 460b2–3 (or follows an interpolated manuscript of the translatio vetus36):37 “our sense-impressions persist, remaining perceptible, even after the external sense-object has gone,” which he renders as follows:
Furthermore, Aristotle states that the sensibles that have been received are stored in a ventricle (a ventricle is a cavity in the brain, as Avicenna says); hence, they do not remain in the organs of the particular senses.38
Earlier in De homine, Albert employs a somewhat less drastic method for reconciling Aristotle’s position with Avicenna’s. When discussing the definition of imagination,39 Albert admits that the sense-organs do have some ability to retain the sensible forms, but that the retentive power of the senses is weaker than that of imagination because, contrary to imagination, the senses can only retain the forms as long as the matter of the sensible object is still present.40
Despite the fact that Aristotle does not anywhere explicitly mention that the sensible species are stored in imagination, De insomniis is adduced several times by Albert as evidence for the vis retentiva of imagination. In his long discussion of the definition of the common sense (De homine, 271.1–274.43), he refers to De insomniis to prove (contrary to Avicenna41) that phantasía and the sensus communis are two distinct faculties:
But the retaining function belongs to phantasía, as the Philosopher states in his work On Sleep and Waking. For there he says that the phantásmata that have been received by the senses remain in phantasía and in sleep they flow back to the sense-organs; hence, phantasía and the common sense are not one and the same power.42
As we have seen, in the Arabic commentators, and in Averroes in particular, Albert finds a description of the mechanisms of the process of dream formation that completes the fragmentary account in Aristotle. The passage from Averroes quoted above on pp. 156–57 describes a full cycle that ends where it started: with the particular senses. But to what extent and in what way are the particular senses involved in the process? Aristotle mentions in De insomniis that they are inactivated in sleep but not unaffected,43 but his remaining account demonstrates that the role of the particular senses in sleep is confined to the task of storing the affections caused by the sense-impressions after the sensible objects are no longer present. Later in De insomniis examples are given of direct sense-impressions in sleep, but these are authentic, external sense-impressions and adduced as examples of phenomena that fall outside the definition of enýpnion.44 Averroes, on the other hand, is clear about the fact that the last stage of dream formation is the stage where the particular senses are moved by the common sense. In his model, it seems that it is via the particular senses that the living being finally “perceives” the dream.45 Albert categorically claims – curiously enough, referring not only to Avicenna and al-Ghazālī but also, as it would seem, to Averroes – that the particular senses are not affected by the reverse movement of the phantásmata, which stops at the organ of the common sense.46 Hence, the cycle in Albert is confined to a process involving the common sense and imagination, leaving the particular sense-organs out of the picture as far as possible and completely out of it in the process in sleep. This becomes even clearer in Albert’s second exposition of De insomniis in his commentary on the Parva naturalia. In the introductory chapter of the first tractatus on De insomniis, Albert states that knowledge of the process of dream formation is a prerequisite for the reader’s understanding of the following treatment and summarises it as follows:
From all this it is evident that the movement of sleep starts where the movement of waking ends, viz., in the treasury of the sensible imaginings, that it reaches the location where waking starts, viz., the first sense organ, and that it is the evaporation of sleep that transports the imaginings from one place [to another].47
As shown, the process described in Averroes and adopted with some modifications by Albert is circular. Albert elaborates on several occasions on the nature of the movement back and forth between the common sense and the imagination: it is an eddy (vertigo) consisting of a forward pulsus and a tractus in the opposite direction.48 Whereas Aristotle’s explanation of the movement of the sensible species from the sense-organs to the archē is tied to the inward flow of the heat of the body in sleep, Albert’s explanation of the process stretches beyond the physiological mechanisms of sleep; the pulsus, he claims, is due to the flow of the spiritus animalis from imagination to the common sense, but the tractus is caused by the sensible forms themselves, which by nature are attracted to imagination:
However, the cause of the forward movement is the motion of the animal spirit and the thin blood [flowing] from the organ of imagination to the organ of the common sense (the blood that is distributed to the organs of the particular senses as nourishment). But the cause of the backward motion are the [sensible] forms’ own movements, because once the forms have been apprehended by the common sense, they travel of their own nature to the organ of imagination.49
At what point in this cycle, then, are the movements of the sense-impressions actualised? Aristotle’s account in Insomn. 3, 461b11–21 describes a process where the answer seems to be in the sense-organs or, at least, somewhere between the sense-organs and the heart, where the fully developed sense-impressions are then also perceived. Albert, on the other hand, seems to assume that the movements are actualised somewhere between imagination and the common sense.50 In his commentary on the Parva naturalia, he describes at great length that differences in this part of the process as the reason why the same forms may be perceived differently by individual sleepers: Different states of body and mind may affect the actualisation of the dream when it travels from imagination and hits the primary sense-organ.51
Albert’s (following Averroes’) identification of the archḗ in De insomniis with the sensus communis is central to his explanation of the process. It is a natural assumption; Aristotle has already stated in Somn.Vig. 2, 455a12–22 that it is by a certain koinḕ dýnamis associated with the particular senses that we are aware that we perceive. In Insomn. 3, 461a27–b5, Aristotle now claims that it is because the stimuli come from the sense-organs to the archē, not only when we are awake but also when we sleep, that we believe that we actually perceive by our senses when we are really dreaming. Hence, the role of the common sense in Albert’s model is to receive the sensible forms from the sense-organs, process them,52 and forward them to imagination, where the phantásmata are formed, then receive the phantásmata again from the imagination and “reflect on them,” comparing them to external sense-impressions.53
But how is this possible? If, as stated by Aristotle in Somn.Vig. 2, 455a33–b2, the reason why our particular senses are deactivated in sleep is that the superior sense-organ is immobilised and this superior sense-organ is the organ of the common sense – how, then, can the common sense also be the faculty processing the phantásmata? Albert’s solution is found in his quaestio on Aristotle’s definition of sleep and wakefulness in De homine. His initial objection to Aristotle’s definition of sleep as an immobilisation of sensation is the following:
Furthermore, sleep does not seem to entail a complete immobilisation of the senses, because the common sense is a kind of sense and it is not immobilised in sleep. A proof of this is that, as Aristotle claims in the second book of On Sleep and Waking,54 the phantásmata flow from the organ of imagination to the organ of the common sense and change it.55
This objection against Aristotle’s definition is refuted with the following solution. The common sense has two relations. One to the external senses in which it inflates these with the spiritus and the sensitive power. In this relation, the organ of the common sense is immobilised in sleep. The other is to the organ of imagination which is situated in a part of the brain that is by nature cold. Hence, in its relation to imagination the common sense is also by nature cold and, consequently, not immobilised in sleep. This is the reason, Albert claims, why Aristotle modifies his definition of sleep in Somn.Vig. as an immobilisation of the senses by saying that it is “a kind” of fetter or immobilisation.56
Whereas the part of the common sense that is closest to imagination stays active in sleep, the anterior part is immobilised, and since this part of the common sense also is where the nerves connect the common sense with the particular sense-organs, the particular senses are immobilised as well.57 As we have seen above, Albert’s position is that the phantásmata never reach the particular senses on their way back from imagination. The argument about the location of the starting-point of the nerves in the common sense is also used by Albert in his commentary on Somn.Vig. to explain Insomn. 3, 461a25–29:58 The reason why we so often believe that we are perceiving when we are actually dreaming is that the phantásmata stimulate the starting-point of the nerves.59
But if the common sense is only partly immobilised in sleep, why does it so often fail to recognise that the phantásmata we see in our dreams are not external sense-impressions but dreams? Aristotle claims that this is due to the power of sleep,60 and Albert agrees and expounds on Aristotle: Not only is the common sense immobilised in sleep in its relation to the external senses, it is also immobilised in its ability to compare the phantásmata that it receives from imagination with external sense-impressions and to distinguish the two.61 Also, Albert notes, although the intellect, unlike the common sense, is not generally immobilised in sleep, it can be immobilised accidentally in two ways: (1) in sleep, the soul aims first and foremost at the movement of imagination and so it happens that it disregards the movements from the intellect,62 and (2) when we are awake, sensory stimuli pass from the external world to the senses, from the senses to imagination and from imagination to the intellect, whereas in sleep, they return to imagination without passing the intellect, which leaves the intellect unaffected.63
When both the common sense is immobilised and the intellect is also accidentally immobilised for any of the two reasons mentioned, the sleeper will be deceived by his dream, believing that he is actually perceiving external stimuli and not dreaming.64 In Albert’s account, the inability of the common sense in sleep to compare sense-impression and distinguish between external sense-impressions and dreams is, contrary to the accidental failure of the intellect, described as absolute.65 Hence, in Albert’s explanation the “something” (
4 Between Albertus Magnus and John Buridan
Among the commentaries here studied that were written between Albert’s expositions and John Buridan’s question commentary, two may be singled out as particularly interesting. One is the question commentary by Geoffrey of Aspall, because as mentioned above and elsewhere,68 unlike the other works here studied, Aspall’s work contains no clear indication that he knows of Albert’s works.69 The other is the commentary by John of Jandun, which, as we shall see, is refreshingly independent in its treatment not only of Aristotle, but also of John’s predecessors’ proposed solutions.
Geoffrey of Aspall devotes considerable attention to the role of the particular senses in the process of dream formation. According to Geoffrey, Aristotle’s remark in Insomn. 1, 459a2–5 that the particular senses are affected in sleep should be understood as referring to the activity of the common sense as the “root” of each of the five particular senses: When the common sense is affected by the phántasma, it is affected “with respect to any of the particular senses,” which is the reason why we so often believe that we are perceiving in our sleep.70 Like Albert, Geoffrey supports Averroes’ description of the process of dream formation, but also just like Albert, he seems to hold that the dreams are perceived by the common sense as the last stage of the process.71
Like Albert, Geoffrey of Aspall refers to de An. 2.5, 417b23–25, in which Aristotle claims that we cannot perceive whenever we choose to, as an objection to Aristotle’s claim that the sense-impressions are stored in the particular sense-organs.72 But whereas Albert waves the argument aside with the less sophisticated comment that Aristotle at this specific instance in De anima has only perception in waking condition in mind, Geoffrey provides several explanations aimed at reconciling the theory put forth in De insomiis with the conclusion in De anima: As Aristotle holds, the sense-impressions can be stored in the sense-organs, but they do not have the capacity to change them and, hence, as stated in De anima, it is not in our power to perceive whenever we choose.73 Furthermore, the simulacra are contained both in the sense-organs and in the common sense, and their movements affect both, but dreams are only generated in the common sense, because in sleep the spiritus does not reach beyond the common sense.74 Interestingly enough, Geoffrey also adds a fallback solution that touches upon the question of the durability of the movements in the sense-organs and keeps the question open:
And they [= the sensible species] do not remain forever in the sense-organs, but eventually disappear, at least in such a way that they cannot [any longer] change the particular senses.75
The argument that the sense-organs have some limited capacity to store the sense-impressions becomes a recurrent solution to the problem of how the particular senses can store sense-impressions. As demonstrated above, Aristotle’s claim that this is the case was regarded as problematic in several aspects. The most important objections seem to have been (1) the remark in De anima that sensation is only possible if the object is present and (2) the question of the capacity of the sense-organs to store sense-impressions in relation to the retentive power of imagination. As mentioned above, Albert had already tried to solve the problem by claiming that the retentive power of imagination was superior to that of the sense-organs.76 This develops somewhat in the later tradition into an “easy come–easy go” argument: The particular senses (contrary to imagination) perceive the sensible species rapidly, and so they also lose them rapidly.77
To my knowledge, Geoffrey of Aspall does not discuss the question of at what stage in the process (and where in the body) the simulacra are actualised. However, his description of the last stage of dream formation seems to indicate that the actualisation takes place somewhere between the imagination in the brain and the common sense in the heart. His account suggests that he understands Insomn. 3, 461b11–21 as referring to the flow of cooled vapours from the brain to the stomach, which according to the Aristotelian model is the material cause of sleep. But Geoffrey’s interpretation of this passage is hardly the decisive point for him; his reading of Aristotle seems rather to be an effect of the fact that he follows the brain-centered model also adopted by Albert.78 However, it is hard to resist the suspicion that Aristotle’s way of describing the blood retracting from the sense-organs to the heart as “descending” to its source and the movements “descending with it”79 was regarded by Geoffrey as support for the interpretation that Aristotle in Insomn., 3, 461b11–21 describes how the common sense perceives the movements only after receiving them from imagination.80
Like Geoffrey of Aspall, John of Jandun agrees with Albert on most major points, but he also presents a number of pro and con arguments and conclusions that are not found in Albert. In the quaestio “utrum species sensibilium remaneant in sensibus in absentia sensibilium” (“whether the sensible species remain in the senses in the absence of the sensible [objects]”),81 the initial objections include several of the standard counterarguments such as, for instance, the reference to de An. 2.5, 417b23–25,82 but before embarking upon refuting the standard objections, John accounts for a number of, as he claims, invalid proofs for Aristotle’s statement that the sensible species are stored in the sense-organs:
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(1) Some claim the following in support of Aristotle: We do not only perceive external sensibles but also make a judgement about them. Perception and judgement cannot take place simultaneously. Hence, the species must be stored in the sense-organs in the time span between the two actions.83 But, John objects, for this proof to hold, it is not enough to refer to the fact that perception and judgement cannot take place simultaneously, one also has to be able to prove that the sensitive power can make a judgement about the sensible object in its absence, and the particular senses are clearly not capable of that.
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(2) Others try to prove that Aristotle is right by claiming that for the sensible species to be able to change the interior senses via the particular, the species have to somehow be attached to the particular senses. But this claim is refuted, John points out, by a comparison with vision: The visible object cannot change the eye without the diaphanous acting as medium. But neither light nor colour remain in the diaphanous after the visible object is gone; still, visual sense-impressions clearly also affect the interior senses after the object is no longer present.84 Furthermore, John adds, apparently a high number of sensible species change the imagination without remaining in the sense-organs; we are able to perceive a sensible object, remember it, and recall it after the object is gone both in the external world and in the particular senses. This would not have been possible unless the species could change imagination also after the object is gone from the particular senses.
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(3) The standard solution that the sense-organs have some limited capacity of storing the species is dismissed by Jandun as a solution that those who are looking for an easy way out of the problem resort to;85 since it would seem that there are observations that speak against such a capacity, we need a solution that explains how it is at all possible for the sense-organs to store sense-impressions. Vision is dominated by water and hearing by air, and in none of these elements do impressions remain.
Having refuted the proofs above – including rather vigorously the standard solution that the retentive capacity of the particular senses is limited –, Jandun suggests the solution that not all sensible species but only those that are unusually strong remain in the particular senses, and that even these unusually strong impressions do so only for a limited time-span. One could postulate, he claims, that in a case where such an unusually strong impression affects one of the senses, the spiritus would be sent in larger quantities to the respective sense-organ. This unusually large quantity of spiritus will make the organ unusually dry and, consequently, enhance its retentive capacity, while the sense-organs are otherwise typically moist and, hence, primarily receptive and not retentive.86 This, according to Jandun, is the phenomenon behind the various examples of continuous perception that Aristotle adduces in Insomn.:
It could also be claimed, that when some excessive sensible, such as, for instance, a bright colour, a sharp light, a loud sound, and so on, changes with great force one of the sense-organs, nature directs more spirit to that location than it would have done had the sensible in question been more proportionate and balanced, and the large quantity of the spirit dries out the sense-organ and diminishes its humidity to such a degree that for a brief time the organ has the power of retaining the species that has been impressed in it by the excessive sensible, which it would not have had if it had been moved by an object of lesser force. That the truth is such is demonstrated by Aristotle’s many experiments […].87
The distinction between the sensible object as the causa in fieri (and not as the causa in esse) of the sensible species in the sense-organs is central to Jandun’s treatment of the problem: The object causes the sensible species to enter the sense-organs, it does not sustain the existence of the species there; hence, the cause can be removed without the effect being removed just as the builder can be removed after the house has been built without the house being destroyed.88
So, can the activity of the common sense in sleep when it is moved by a phántasma be described as a kind of perception? Aristotle seems to believe so.89 John of Jandun explicitly and without modification describes the activity of the common sense as a sensation; more precisely, it is, according to John, the type of sensation that Averroes in his commentary refers to as “spiritual”:
And this sensation that the common sense performs when it is changed by the images that have been stored internally is the one that the Commentator in the beginning of his treatise calls “spiritual,” that is, the object that changes the common sense is something spiritual, viz. an image of some things and stored internally, and when the common sense senses in this way, he calls it a sense in potentiality, because it is not changed per se by the action of external things that move the particular senses, but is only in potentiality with respect to such a change, although it is actually changed by the internally stored likenesses of things.90
Albert’s explanation in De homine that the common sense has two comparationes and is immobilised only with respect to one of them is found in the majority of the commentaries here studied. Geoffrey of Aspall resorts to it on the same two occasions as Albert: in a quaestio on Aristotle’s definition of sleep91 and when dealing with the problem whether sleep and waking are affections of the common sense.92 James of Douai, among others, adduces it as evidence that dreaming is an affection of the common sense.93 However, for none of the commentators here considered does the solution with the two relations of the common sense manage to solve the problem of sleepwalking, where not only some perception is possible in sleep but where there is also the ability to move while the common sense is inactivated.94
5 John Buridan
When Buridan enters the scene in the first half of the fourteenth century, he brings with him the first major shift from the earlier tradition by not accepting the standard arguments for locating the common sense in the brain. Instead he supports Aristotle’s claim that its real location is in the heart. Buridan’s arguments for the location of the common sense will not be discussed in detail here; it has already been dealt with extensively by others.95 A few studies have also very briefly touched upon the implications of Buridan’s theories on the structure of the brain and the nature and function of the interior senses on dream formation,96 but research on the topic is so far very limited.
In Peter G. Sobol’s inventory of the content of Buridan’s question commentary on De anima 2, the following deviations from the earlier tradition may be noted as the most relevant here: According to Buridan, (1) the sensible species travel from the external senses directly to the brain via nerves in the anterior part of the brain and then from the brain to the organ of the common sense in the heart, and (2) dreams are a result of sensible species traveling via a nerve from the organ of memory in the back of the brain to the organ of the common sense in the heart.97 Buridan adduces two reasons for (1), which both involve protecting the heart: The heart is sensitive to excessive stimuli; hence, the sensible species travel not directly to the heart but via the brain in order to protect the heart by slowing down the impetus passionis. But the heart must also be protected against exhaustion from emitting the spiritus sensibilis to the exterior senses when we are awake; hence, there has to be a mechanism to cut off the flow of the spiritus and the brain is the most suitable location for this mechanism because the hot vapours from food gather in the cold brain and thicken because of its coolness.98
Buridan’s question commentary on the Parva naturalia contains only two questions directly related to De insomniis.99 One is the question whether dreams are always generated in sleep,100 the other one discusses the validity of Aristotle’s definition of dreaming.101 The former does not add much to the topic discussed here,102 but the latter pinpoints – but does not solve – a question that arises from (2) above: According to Aristotle, both dreams and memories are generated from remnants of sense-impressions that remain in the body after the sensible object is gone. However, contrary to dreams, memories come with a consciousness that they are of the past.103 Now if dreams are generated from sensible species traveling from memory to the heart, why are we not conscious that our dreams are sense-impressions of the past? The earlier tradition, including Aristotle himself, has categorically refrained from describing dreams as made of memories, in all likelihood precisely because in our dreams we typically believe that we are perceiving the present.
Buridan’s quaestio on Aristotle’s definition of enýpnion in his question commentary on Somn.Vig. does not address this problem directly, but it contains an account of four types of apparitiones that proves to be relevant in this connection. Only one of these types of apparitions – or rather a subcategory of one category – is properly called dream:104
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(1) Apparitiones sensuales: external sense-impressions in sleep as examplified by Aristotle in Insomn. 3, 462a19–27, which are simply perception that occurs when sleep is weak.105
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(2) Apparitiones intellectuales: what Aristotle calls alētheîs énnoiai (
ἀληθεῖς ἔννοιαι ) in Insomn. 3, 462a28, “true thoughts” that do not only occur when we are awake but occasionally also when we sleep, -
(3) Apparitiones phantasticae: apparitions caused by the sensible species that are stored in imagination and appear to the common sense when we are awake, as, for instance, when we imagine a place even though we are not there, or when small children imagine terrifying things because they are afraid of the dark. When apparitions of this type appear in our sleep, we call them dreams.106
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(4) Apparitiones memorativae: Contrary to the sensible species stored in imagination, species stored in memory are stored cum certa differentia temporis. Hence, type (3) apparitions will typically appear to us as something that we are perceiving in the present, whereas type (4) will appear as something we perceived in the past.107
Buridan points out that type (3) is more common than (4) and that it is only apparitions of type (3) that are properly called dreams.108 Hence, the distinction between memory and dream is also clear enough here: Memories, viz. sensible species stored in memory “with a certain time-distinction” (cum certa differentia temporis), can occasionally appear to the common sense also in sleep, but only the sensible species that are stored in imagination “without a certain time-distinction” (sine certa differentia temporis) are authentic dreams109 and these are, contrary to memories, always false, in the sense that they appear to us as something we perceive in the present, even though they are not.110
6 Conclusion
At least on the basis of the texts here studied, one may conclude that the medieval Latin commentary tradition on Aristotle’s theories of dreaming is clearly limited compared to the interest in the physiological aspects of sleep as put forth in De somno et vigilia. Nevertheless, the Latins obviously found some problems in Aristotle’s theory on dream formation worth exploring, no doubt because they proved to have considerable bearing on the fundamental question of the structure of the soul as well as on the interrelation of sense-perception, imagination, and cognition. The question of the retentive capacity of the sense-organs finds no convincing solution in the commentators here discussed and some new problems surface as the tradition develops, such as the question of the interrelation of dreams and memories. On the other hand, the thirteenth- and fourteenth-century Latin commentators managed – with much help from the Arabs – to make a few not unimportant contributions to the reception of Aristotle’s psychology, such as a considerably more complete theory of the process of dream formation as well as some substantial clarifications of the ambiguous role of the common sense in dreaming.
See below, 155; note James of Douai, Expositio cum quaestionibus super libros De somno et vigilia, edited by Sten Ebbesen in “James of Douai on Dreams,” Cahiers de l’Institut de Moyen-Âge Grec et Latin 84 (2015): 22–92, here 50.11–18. In the medieval reception, all three treatises on sleep and dreams by Aristotle circulated under the title of the first work, and De insomniis was usually considered to be the second book of the work; hence, the abbreviation Somn.Vig. here and in all other titles of medieval works in this chapter represents not only De somno et vigilia but also De insomniis and De divinatione per somnum.
On the chronology of Albert’s works, see vol. 1, 185n7.
On the quaestiones of Aspall, Jandun, Faversham, Buridan, the two question commentaries in the Rome manuscript, and the expositio by Burley, all referred to in this chapter, see vol. 1, 200–201nn58–66. For Douai, see Olga Weijers et al., Le travail intellectuel à la Faculté des arts de Paris: Textes et maîtres (ca. 1200–1500) (Turnhout: Brepols, 1994–2012), 4:100–103, and Sten Ebbesen, Christina Thomsen Thörnqvist, and Véronique Decaix, “Questions on De sensu et sensato, De memoria and De somno et vigilia,” Bulletin de Philosophie Médiévale 57 (2015): 102–3. For Brito, see Weijers, Le travail intellectuel, 8:43–64, and Ebbesen, Thomsen Thörnqvist, and Decaix, “Questions,” 107–8. A selection of Brito’s quaestiones has been edited in Sten Ebbesen, “Radulphus Brito on Memory and Dreams: An edition,” Cahiers de l’Institut de Moyen-Âge Grec et Latin 85 (2016): 11–86. I have checked also the question commentary by Peter of Auvergne (d. 1304), but it proved to contain nothing of relevance to the issue here discussed. On Peter’s commentary, see vol. 1, 200–201n61.
See Somn.Vig. 2, 455a12–33; 3, 458a25–32.
See Somn.Vig. 1, 454b9–11.
See Somn.Vig. 2, 455a9–12.
See Insomn. 2, 459a28–b7. For the movement described as a chain-reaction, cf. de An. 3.3, 428b10–17.
Insomn. 3, 461a3–8.
Insomn. 3, 461a11–25.
See above, 154n16.
See Insomn. 3, 461b16–21 (154n18).
Insomn. 3, 461a25–b5 (154n13).
See Insomn. 3, 461b25.
Insomn. 3, 461b26–29:
On the date of Adam’s commentary, see vol. 1, 185n6.
See vol. 1, 185.
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.
“Dicendum quod sicut dicit Alfarabius, in vigilia motus sensibilium est a sensu in imaginatione, ita quod principium est a sensu et finis in imaginatione. In somnio autem motus est sensibilium praeacceptorum ab imaginatione ad sensum, ita quod principium est ab imaginatione et finis ad sensum, et ideo somnium est imaginationis ut a quo est principium motus eius.” (Albert the Great, De homine, ed. H. Anzulewicz and J. R. Söder (Münster: Aschendorff), 359.4–10.)
“In vigilia enim sensibilia extrinseca movent sensus, et sensus communis movet virtutem ymaginativam. In sompno autem, quando virtus ymaginativa ymaginata fuerit intentionem quam accipit ab extrinseco aut ex virtute rememorativa, revertetur et movebit sensum communem, et sensus communis movebit virtutem particularem; et sic accidit quod homo comprehendit sensibilia, licet non sint extrinsecus, quia intentiones eorum sunt in instrumentis sensuum, et indifferenter, sive intentiones veniant ab extrinseco, sive ab intrinseco.” (Averroes, Compendia librorum Aristotelis qui Parva naturalia vocantur, ed. A. L. Shields (Cambridge, MA.: Medieval Academy of America, 1949), 98.69–99.9.) The translation is quoted from 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), 189.
Albert the Great, De hom., 366.65–368.40.
Albert the Great, De hom., 368.4–8.
Albert the Great, De hom., 368.9–11; the reference to Avicenna is probably to Liber De anima seu Sextus de naturalibus, ed. S. van Riet (Louvain: Peeters, 1968–72), 2:4.1, 4.45–52. “Imagines autem quae videntur in somnis, aut fiunt ex descriptione formae in thesauro retinente formas […], aut contingunt ex alia virtute, quae est aut sensus exterior aut interior: sed sensus exterior non prodest in somnis, quia aliquando qui imaginat colores est privatus oculis. Restat ergo ut hoc fiat in sensu interiore.”
See, for instance, Albert the Great, De hom., 275.11–15.
On the encephalocentric theory in the Arabic tradition, see Donati, “Albert the Great as a Commentator,” 181–84.
According to Drossaart Lulofs’ edition of the translatio vetus of Insomn. (Aristotelis De Insomniis et De divinatione per somnum, ed. H. J. Drossaart Lulofs (Leiden: Brill, 1947)), the St. Florian manuscript XI 649 (twelfth century) has the addition “in cella” after “extrinsecus” on 16.11.
“Praeterea dicit Aristoteles quod accepta sensibilia manent in cella; cella autem est concavitas cerebri, ut dicit Avicenna; ergo non manent in organis sensuum propriorum.” (Albert the Great, De hom., 367.63–66.) The reference is to Avicenna, Liber Sextus, 1:1.5, 87.19–88.25: “Virium autem apprehendentium occultarum vitalium prima est fantasia quae est sensus communis; quae est vis ordinata in prima concavitate cerebri, recipiens per seipsam omnes formas quae imprimuntur quinque sensibus et redduntur ei. Post hanc est imaginatio vel formans, quae est etiam vis ordinata in extremo anterioris concavitatis cerebri, retinens quod recipit sensus communis a quinque sensibus et remanet in ea post remotionem illorum sensibilium.”
Albert the Great, De hom., 282.10–17.
“[…] dicendum quod licet sensus recipiat formas tales, et similiter imaginatio, tamen sensus proprie diffinitur per recipere, et imaginatio per retinere, vis enim retentiva debilis est in sensu, eo quod non retinet nisi praesente materia, sed vis receptiva fortis, eo quod de facili recipit, sed e contrario est in imaginatione.” (Albert the Great, De hom., 284.58–64.)
See above, n. 38.
“Sed phantasiae est retinere, ut dicit Philosophus in libro De somno et vigilia. Dicit enim ibi quod simulacra recepta a sensibus manent in phantasia et refluunt in somniis ad organa sensuum; ergo phantasia et sensus communis non sunt eadem virtus.” (Albert the Great, De hom., 272.9–14.) In this connection, Albert also refers to the mechanisms of dream formation in Insomn. to provide an etymological explanation for “imaginatio”: “Quandoque etiam dicitur imaginatio vis, a qua refluunt imagines repositate super organum sensus communis, et sic accipitur ab Aristotele in secundo de somno et vigilia, ubi dicit quod in somno imagines somniales refluunt ad commune organum sensuum.” (Albert the Great, De hom., 284.24–28.)
See, in particular, Insomn. 3, 462a15–31.
See also the Versio Parisina in Shield’s edition (98–99): “Sicque sompnium secundum diversitatem formarum compositarum apud ymaginacionem, sicut videmus in infirmis (in quibus vapores resolvuntur ad cerebrum a materia morbi; in quibus vaporibus ymaginativa componit formas terribiles, quas infirmus eciam vigilans iudicat se videre extra; et tamen videt eas intra), predicto modo, quia videlicet ymaginativa offert eas sensui communi et sensus communis offert eas sensibus particularibus.” On the two versions of Averroes’ Compendium, see David Bloch, Aristotle on Memory and Recollection: Text, Translation, Interpretation, and Reception in Western Scholasticism (Leiden: Brill, 2007), 154.
“Ad aliud dicendum quod quidam dicunt quod sensus etiam proprii immobiles quidem sunt in somno secundum actus exteriores, interius autem a quodam calore interiori solvuntur. Sed hoc non placet, sed potius secundum Alfarabium et Avicennam et Algazalem dicendum est quod motus somnii sistit ad organum sensus communis.” (Albert the Great, De hom., 361.53–59.) See ibid., 362.19–24 and 366.45–61, and note Albert’s argument on 360.42–55 that since the sense-organs are homogenous substances, one part of them cannot be affected by motion without also the rest of the organ being affected; hence, the sense-organs cannot be immobilised externally but mobile internally; cf. PA 2.1, 647a.
“Ex quibus omnibus constat, quod motus somni incipit ubi terminatur motus vigiliae, scilicet in thesauro imaginationum sensibilium, et provenit ad locum ubi incipit vigilia, hoc est ad primum organum sensuum, et quod evaporatio somni vehit eas ab uno loco in alium.” (Albert the Great, De somno et vigilia, ed. A. Borgnet (Paris: Vivès, 1890), 2.1.1, 159a.)
See, for instance, Albert the Great, De hom., 361.22–34.
“Causa autem pulsus est motus spiritus animalis et subtilis sanguinis ab organo imaginationis ad organum sensus communis, qui sanguis distribuitur in alimentum organorum sensuum propriorum. Causa autem tractus proprius motus est ipsarum formarum; formae enim apprehensae a sensu communi secundum suam naturam transeunt ad organum imaginationis.” (Albert the Great, De hom., 372.29–36.) Surprisingly enough, Albert refers to Aristotle’s metaphor for explaining the actualisation of the movements in Insomn. 3, 461b15–17 as support for the explanation of the pulsus caused by the spiritus animalis; see Albert the Great, De hom., 371.65–77: “Cum autem ipse spiritus deferens formas sit de natura humidi aërei et feratur cum humido et subtili sanguine quasi vaporabili, dicit Philosophus quod motus simulacrorum in ipso est sicut motus ramunculorum liquefacti salis in aqua calida. Cum enim aqua calida liquefit sal, subtilis elevatur sursum ex calido movente et humido liquante sicut ramunculus albus, et postea iterum residet ex natura gravis, quae est in terrestritate salis. Similiter formae imaginationis descendunt descendente spiritu et sanguine ab imaginatione ad sensum communem et revertuntur iterum ad cellam imaginationis tamquam ad locum proprium, in quo habent commanere.”
It should be noted that this interpretation is found already in Adam of Buckfield: “Deinde cum dicit cum enim manifestat similitudinem hanc, dicens, quod in dormiendo descendit multus sanguis ad primum sensitivum, et simulacra similiter in ipsis propriis organis descendunt ad primum sensitivum, et movent ipsum: alia quidem movent in actu, sicut illa, quae proxima sunt, alia autem movent solum in potentia, quae non devenerunt ad primum sensitivum.” (Adam of Buckfield, Commentarium in De somniis, edited in Doctoris angelici divi Thomae Aquinatis opera omnia XXIV, ed. S. E. Fretté (Paris: Vivès, 1875), l. 4.) Note that Albert locates the refigurations of the movements “because of obstruction” (Insomn. 2, 461a8–11) to the head: “Haec autem corruptio fit propter repercussionem vaporis ad concavum capitis, ex quo reflectitur necessario in seipsum, et non tenet figuram in qua ascendit […] eo quod multus motus vaporationis fortiter repercutitur ad craneum, et in seipso refractus non tenet imagines.” (Albert the Great, De somno, 2.2.1, 170a.) A particular variant of refiguration of the simulacra is described by John of Jandun: sometimes more than one simulacrum will reach the common sense simultaneously and combine into images of composite objects that we have never perceived with our external senses, such as a living being with the head of a horse but the body of a man; see John of Jandun, Ioannis Gandavensis philosophi acutissimi Quaestiones super Parvis naturalibus, ed. A. Apulus (Venice: Hieronymus Scotus, 1557), fol. 43va, and cf. Radulphus Brito, Quaestiones super librum De somno et vigilia, partial edition in Sten Ebbesen, “Radulphus Brito on Memory and Dreams: An Edition,” Cahiers de l’Institut du Moyen-Âge Grec et Latin 85 (2016): 11–86, here 65.
“[…] et talium motuum simulacrorum quidam sunt potestate, alii vero actu: potestate quidem qui possunt elici ex figura vaporis propter aliquam convenientiam, praecipue ab eo qui passione aliqua detentus est: actu vero sicut illae quae a sensibus acceptae sunt imagines, et refluunt ad organorum principia.” (Albert the Great, De somno 2.2.2, 172a.) In this connection, Albert also provides an alternative interpretation of Insomn. 3, 461b11–21 which is considerably closer to Aristotle; see ibid., 2.2.2, 172a–b.
See, in particular, de An. 3.2, 426b8–427a15; Albert the Great, De anima, ed. C. Stroick (Münster: Aschendorff, 1968), 161.68–165.82; De hom., 278.32–281.77.
See, e.g., Albert the Great, De hom., 368.12–31; 371.55–372.6.
However, see above, p. 155.
“Praeterea, somnus non videtur universaliter immobilitas sensus. Sensus enim communis est quidam sensus; et ille non immobilitatur in somno. Cuius probatio est haec quod dicit Aristoteles in secundo De somno et vigilia quod phantasmata fluunt ab organo phantasiae ad organum sensus communis et immutant ipsum.” (Albert the Great, De hom., 319.25–30.) The reference to Insomn. must be to 3, 461a6.
“Ad aliud dicendum quod sensus communis duplicem habet comparationem. Unam ad sensus exteriores, quibus ipse influit spiritum sensibilem et virtutem sensitivam, propter quod etiam dicitur ab Avicenna forma et perfectio sensuum particularium; et in hac comparatione ligatur organum eius, et somnus est vinculum sensus communis. Aliam habet comparationem ad organum phantasiae et imaginationis, quae sitae sunt in partibus cerebri, quae naturaliter frigidae sunt, et ideo frigiditate quae dominatur in somno, non immobilitantur, et cum organum sensus communis in comparatione illa etiam sit frigidum per naturam, non immobilitabitur in somno sed immutabitur simulacris refluentibus a loco phantasiae et imaginationis. Et hoc intendit Philosophus, quando dixit somnum esse vinculum quodammodo sensum.” (Albert the Great, De hom., 322.5–20.) For Albert’s reference to Aristotle, see Somn.Vig. 1, 454b10–11 (
“Et in prima comparatione nervi sensibiles, qui terminantur in organis sensuum propriorum, principiantur in organo sensus communis, et ideo frigiditas descendens a cerebro primo tangit nervos sensibiles in sui principio, quod est anterior pars sensus communis, et immobilat ipsos et oppilat non permittendo spiritum sensibilem ab organo sensus communis fluere in nervos sensibiles.” (Albert the Great, De hom., 333.15–22.) On the explanation that an immobilisation of the starting-point of the nerves in the heart is the reason why the particular senses are immobilised in sleep, see Averroes, Compendium, 87.14–19. For Albert’s version of the three-cell structure of the brain, where each of the three cells in turn is divided into two compartments, see, for instance, Albert the Great, De animalibus libri XXVI, Nach der Kölner Urschrift, ed. H. J. Stadler (Münster: Aschendorff, 1916), 1:187.40–188.3: “Adhuc autem cerebrum secundum suam longitudinem tres habet ventres, quorum quilibet per latitudinem suam duas habet partes, dextram videlicet et sinistram propter lineam quae per longum dividitur.” On the location of the sensus communis next to imagination in the anterior ventricle, see, e.g., Albert the Great, De anima, 158.4–33. Also, see Christopher Upham Murray Smith, The Animal Spirit Doctrine and the Origins of Neurophysiology (New York: Oxford University Press, 2012), 76–77; Peter Theiss, “Albert the Great’s Interpretation of Neuropsychiatric Symptoms in the Context of Scholastic Psychology and Physiology,” Journal of the History of the Neurosciences 6 (1997): 240–56, esp. 250; Christopher Upham Murray Smith, “Beginnings: Ventricular Psychology,” in Brain, Mind and Consciousness in the History of Neuroscience, ed. C. U. M. Smith and H. Whitaker (Dordrecht: Springer, 2014), 8–11.
See 154n13, above.
“Ex eo enim quod discreto sanguine progreditur talis motus simulacrorum ad sensum communem, ubi contingunt se nervi sensibiles, quod est principium vigilandi, sicut saepe diximus, videtur sibi somnians videre et audire et omnia universaliter sentire. Videtur autem decipi ex hoc quod visus videtur moveri, qui non movetur a re sensibili aliqua, sed est forma motus in eo ipso.” (Albert the Great, De somno 2.2.2, 171a–b.) Note also that according to Albert the refiguration of the movements in Insomn. 3, 461a8–11 takes place in the head and affects not the stimuli coming from the sense-organs but the phantásmata flowing from imagination to the common sense: “Saepe enim vehitur imaginatio vecta in sua propria similitudine ad principium sensus, et saepe corrumpitur in alias figuras propter fluxum humidi spiritualiter evaporantis, quae deferunt formas phantasiae: corrupto enim subjecto, necesse est corrumpi figurationem formae quae in ipso est. Haec autem corruptio fit propter repercussionem vaporis ad concavum capitis, ex quo reflectitur necessario in seipsum, et non tenet figuram in qua ascendit: haec enim est causa, quod immediate post multum nutrimentum, et praecipue si calidum sit, et multum vaporativum, non fiunt somnia: eo quod multus motus vaporationis fortiter repercutitur ad craneum, et in seipso refractus non tenet imagines.” (Albert the Great, De somno, 170a.)
See Insomn. 3, 461b30.
Albert the Great, De hom., 379.14–18.
Albert the Great, De hom., 379.20–28.
Albert the Great, De hom., 379.29–40.
Albert the Great, De hom., 379.37–40.
“Sensus enim communis licet non immobilitetur in somno quoad actum interiorem, tamen immobilitatur quoad exteriorem et quoad comparationem interioris ad exteriorem; et hoc dicitur maior potentia somni.” (Albert the Great, De hom., 379.14–18.)
See above, 155n23.
“Quando autem sensus communis interius comparat ad exterius, tunc contingit ex debilitate dormitionis, quia iam sensus communis quodammodo incipit solvi ad actum exteriorem.” (Albert the Great, De hom., 379.78–380.1.)
See vol. 1, 202.
See 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): 261.
“Unde quod dicit Aristoteles quod sensus patiuntur in somno, hoc intelligendum est non in se sed in sua radice, ut in sensu communi […].” (Geoffrey of Aspall, Quaest. Somn.Vig., 320.) Also, see ibid., 326.
Geoffrey of Aspall, Quaest. Somn.Vig., 329 (see, in particular, 2.2: “apud somnum non moventur sensus particulares”), and 330.
Cf. James of Douai, Quaest. Somn.Vig., 55.18–20, 56.18–21.
Geoffrey of Aspall, Quaest. Somn.Vig., 323.
Geoffrey of Aspall, Quaest. Somn.Vig., 326.
“Nec etiam semper manent [sc. species sensibilium] in organis sensitivis, sed tandem evanescunt, ad minus ita quod non possunt ipsum sensum particularem <immutare>.” (Geoffrey of Aspall, Quaest. Somn.Vig., 323.) Note that James of Douai also comments on the duration of the movements caused by the sense-impressions, referring, as Ebbesen points out, to Ph. 8.10, 267a5–9: “Unde tamdiu continuatur motus proiectionis quamdiu virtus primi moventis est fortior et motus eius est fortior quam sit motus naturalis proiecti, et illud latius dictum est in VIII° Physicorum.” (James of Douai, Quaest. Somn.Vig., 51.22–24.)
Cf. James of Douai, Quaest. Somn.Vig., 50.29–31: “Nam si species sensibilium manent in sensibus abeuntibus sensibilibus et in absentia ipsorum, multo fortius et species sensibilium manebunt in sensibus interioribus in absentia sensibilium, sicut in phantasia.” Albert’s position is reflected in his tendentious interpretation of Insomn. 2, 459b7, where Aristotle is explicitly refering to the sense-organs (Insomn. 2, 459b5–7:
See James of Douai, Quaest. Somn.Vig., 55.28–56.2.
See Donati, “Albert the Great as a Commentator,” 183–84, on Geoffrey’s discussion of the location of the internal senses, including the disagreement between Aristotle and the Arabic tradition.
Insomn. 3, 461b11–12:
“Et praeter hoc, Aristoteles inferius, ubi determinat modos quibus moventur ista simulacra ad organum sensus communis, dicit quod sedata turbatione sanguinis, ut post digestionem, tunc descendunt simulacra a partibus superioribus, ut a cerebro, usque ad cor; ergo secundum Aristotelem ista simulacra secundum quae fiunt somnia non currunt sive fluunt ab organis exterioribus sed ab interioribus.” (Geoffrey of Aspall, Quaest. Somn.Vig., 329.) Cf. James of Douai, Quaest. Somn.Vig., 65.11–30.
John of Jandun, Quaest. Somn.Vig., fol. 42va–43rb.
John of Jandun, Quaest. Somn.Vig., fol. 42va, 43ra; cf. Radulphus Brito, Quaest. Somn.Vig., 58, 60; Simon of Faversham, Quaestiones super librum De somno et vigilia, ed. S. Ebbesen, in “Simon of Faversham, Quaestiones super librum De somno et vigilia: An Edition,” Cahiers de l’Institut de Moyen-Âge Grec et Latin 82 (2013): 137, 139; Walter Burley, Expositio in Aristotelis De somno et vigilia, ed. C. Thomsen Thörnqvist, in “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): 489.13–16, 491.14–26. A recurrent objection is also the comparison between the external senses and a mirror: the relation between the sensible form and the external senses is equivalent of that of a form seen in a mirror and the mirror itself, because when the sensible object is removed, the impression of it on the senses/the mirror also disappears. The standard argument against the simile is that while it is true that both in the eye and in the mirror the sensible species represents that of which it is a species, since the mirror, contrary to the eye, does not have a soul, it does not have cognitive power and so also lacks the ability to make a judgement about the species, whereas the senses have not only the ability to perceive the species but also to make a judgement about it, and so must also have the ability to preserve it (James of Douai, Quaest. Somn.Vig., 55.15–17, 56.13–17; John of Jandun, Quaest. Somn.Vig., fol. 42va, 43ra; Anonymus Angelicani, Quaest. Somn.Vig., MS Rome, Bibl. Angelica, 549, fol. 109rb; Radulphus Brito, Quaest. Somn.Vig., 58, 59–60; Simon of Faversham, Quaest. Somn.Vig., 137, 138–39; Walter Burley, Exp. Somn.Vig., 489.9–12, 491.8–13). Note that Burley (491.8–13) differs from the other three by (with some hesitation) suggesting the less sophisticated explanation that the mirror receives the impression only on its surface, whereas the eye receives it in its depth and so preserves it longer than the mirror.
See John of Jandun, Quaest. Somn.Vig., fol. 42vb. The argument which is ascribed to “aliqui” is found in Brito, Quaest. Somn.Vig., 58–59.
“Et ideo alii dicunt aliter, quod per species inexistentes sensibus particularibus sensus particulares immutant uirtutes interiores et ideo oportet, quod species ipsae habeant aliquam fixionem et permanentiam in sensibus particularibus.” (John of Jandun, Quaest. Somn.Vig., fol. 42vb.) John (fol. 42vb) refers to Albert for this argument (“istam rationem tangit Albertus”); the reference must be to Albert the Great, De somno, 164a (“et remanet forma per spatium in organo sensus postquam alteratum est: quia aliter secundum illam formam non moveret interiores animae partes et organa”).
“Aliqui breviter se expediunt et dant causam huius, quod organa sensuum non solum habent potentiam receptivam specierum sensibilium, sed etiam virtutem conservativam et virtutem retinendi ad aliquod tempus.” (John of Jandun Quaest. Somn.Vig., fol. 42vb.)
See also John of Jandun, Quaest. Somn.Vig., fol. 42va, where the objection to Aristotle’s position is adduced that the conclusion that the sense-organs can both receive and store the species presupposes that the disposition of the organs is both dry (retentive) and moist (receptive) at the same time, and since dry and moist are contraries, this is not possible. Jandun here refers to Averroes on Mem.: “siccitas enim innata est recipere difficile; et cum receperit formam, tunc innata est retinere eam longo tempore; econtrario de humido” (Averroes, Compendium, 70.39–41); cf. Radulphus Brito, Quaest. Somn.Vig., 58, 60; Simon of Faversham, Quaest. Somn.Vig., 137; Walter Burley, Exp. Somn.Vig., 490.21–491.7; also, cf. Albert on the retentive power of the soul: Albert the Great, De hom., 283.26–31.
“Posset quoque dici quod cum aliquod excellens sensibile, ut puta fortis color uel fortis lux et sonus fortis et sic de aliis, immutat multum efficaciter organum alicuius uirtutis: tunc natura mittit ad locum illum multos spiritus plus quam si illud sensibile esset magis proportionatum et temperatum, et isti spiritus in multitudine pervenientes ad illud organum aliqualiter caliditate sua desiccant illud organum, uel eius humiditatem remittunt in tantum, quod ad aliquod paruum tempus habet illud organum uirtutem conseruandi speciem sibi impressam ab illo sensibili excellenti, quam non haberet si ab obiecto minoris efficaciae moueretur. Quod autem ueritas sic se habeat, quod species sensibilium remaneant Aristoteles multis experimentis ostendit […].” (John of Jandun, Quaest. Somn.Vig., fol. 43ra.)
“[…] non oportet quod causa in fieri remota tollatur effectus, ut domificator est causa domus in fieri et remoto domificatore non oportet domum corrumpi, licet oporteat domificationem cessare […].” (John of Jandun, Quaest. Somn.Vig., fol. 42ra.) Jandun (fol. 43ra) also adds the standard solution to the problem of water and air as the dominating elements in vision and hearing, viz. the distinction between the material eye (which does not have retentive capacity) and vision as a cognitive faculty (which does); cf. James of Douai, Quaest. Somn.Vig., 56.8–12; Anonymus Angelicani, Quaest. Somn.Vig., fol. 109va–b; Radulphus Brito, Quaest. Somn.Vig., 59–60; Simon of Faversham, Quaest. Somn.Vig., 138.
See, for instance, Somn.Vig. 2, 456a24–27; Insomn. 1, 458b29–33; 3, 462a2–5.
“Et illa sensatio sensus communis, quam facit cum immutatus est ab imaginibus interius reseruatis est illa, quam Commentator in principio sui tractatus uocat spiritualem, scilicet obiectum immutans sensum communem est quid spirituale, scilicet imago rei interius reseruata, et sensum communem sic sentientem uocat sensum in potentia, quia per se non immutatur actu a rebus exterioribus mouentibus sensus particulares, sed solum est in potentia respectu talis immutationis, licet a rerum simulacris interius conseruatis actualiter immutentur.” (John of Jandun, Quaest. Somn.Vig., fol. 37ra.) The reference is to Averroes, Compendium, 25.31–27.3, but see also 75.10–77.27. On 25.31–27.3, see Jean-Baptiste Brenet, “Agent Sense in Averroes and Latin Averroism,” in Active Perception in the History of Philosophy: From Plato to Modern Philosophy, ed. J. F. Silva and M. Yrjönsuuri (Dordrecht: Springer, 2014), 158–60.
Geoffrey of Aspall, Quaest. Somn.Vig., 288; cf. Albert the Great, De hom., 322.5–20.
Geoffrey of Aspall, Quaest. Somn.Vig., 298; cf. Albert the Great, De hom., 333.13–50.
James of Douai, Quaest. Somn.Vig., 47.2–19; also, see ibid., 46.1–11. Cf. John of Jandun, Quaest. Somn.Vig., fol. 42va; Siger of Brabant(?), Quaestiones in Aristotelis De somno et vigilia, MS Rome, Biblioteca Angelica, 549, fol. 102rb/MS Munich, BSB, clm. 9559, fol. 48ra; Anonymus Angelicani, Quaest. Somn.Vig., fol. 109rb; Walter Burley, Exp. Somn.Vig., 484.9–13.
Somn.Vig. 2, 456a24–27. For an overview of the medieval discussion of Aristotle’s remark on sleepwalking, see Christina Thomsen Thörnqvist, “Sleepwalking Through the Thirteenth Century: Some Medieval Latin Commentaries on Aristotle’s De somno et vigilia 2, 456a24–27,” Vivarium 54 (2016): 286–310.
The standard argument for placing the common sense in the brain was based on the fact that different injuries to the head resulted in corresponding psychological defects. For Buridan’s position in relation to the earlier tradition, see, for instance, Simo Knuuttila, “Aristotle’s Theory of Perception and Medieval Aristotelianism,” in Theories of Perception in Medieval and Early Modern Philosophy, ed. S. Knuuttila and P. Kärkkäinen (Dordrecht: Springer, 2008), 12; Peter G. Sobol, “John Buridan on External and Internal Sensation,” in Questions on the Soul by John Buridan and Others: A Companion to John Buridan’s Philosophy of Mind, ed. G. Klima (Cham: Springer, 2017), 103–4; Egbert Bos and Stephen Read, Concepts: The Treatises of Thomas of Cleves and Paul of Gelria: An Edition of the Texts with a Systematic Introduction (Louvain: Peeters, 2001), 34–35.
See, for instance, Peter G. Sobol, “Sensations, Intentions, Memories, and Dreams,” in The Metaphysics and Natural Philosophy of John Buridan, ed. J. M. M. H. Thijssen and J. Zupko (Leiden: Brill, 2001), 183–98; id., “John Buridan on External and Internal Sensation,” 104.
Peter G. Sobol, John Buridan on the Soul and Sensation: An Edition of Book II of his Commentary on Aristotle’s Book on the Soul with an Introduction and a Translation of Question 18 on Sensible Species, PhD diss. (Indiana University, 1984), qu. 24, 390–409; Sobol, “John Buridan on External and Internal Sensation,” 104–5. Note Buridan, Quaest. de An. II, qu. 24, 406: “Et notandum est quod aliquando utraque via est clausa, scilicet cordis tam ad organum anterioris capitis quam ad organum posterioris. Et tunc fit nobis sompnus sine sompnio. Aliquando clausa est via ab organum anteriori, manente alia via aliqualiter aperta que est ad organum posterioris, et tunc fiunt sompnia cum nondum valeat fieri sensatio per sensus exteriores.”
Se John Buridan, Quaest. de An. II, qu. 24, 404–5.
The standard question on the retentive power of the sense-organs is not included in the section on Insomn., but scattered remarks in his question commentary on De anima indicate that he, like his predecessors, follows Aristotle in granting the external senses such a power, but adds the aspect that the capacity is very limited in comparison to the retentive power of the common sense and even more so in comparison to that of imagination. See, for instance, Quaest. de An. II, qu. 18, 284; qu. 22, 368.
John Buridan, Quaest. Somn.Vig., qu. vii(2), fol. XLVIrb–vb.
John Buridan, Quaest Somn.Vig., qu. vii(1), fol. XLVvb–XLVIrb. (Note that in Lockert, both quaestiones on Insomn. are numbered “VII.”)
For an account of the causes of dreamless sleep, however, see John Buridan, Quaest. Somn.Vig., qu. vii(2), fol. XLVIva–vb.
See, for instance, Mem. 1, 449b24–30 (edited by David Bloch in Bloch, Aristotle on Memory, 26):
See John Buridan, Quaest. Somn.Vig., qu. vii(1), fol. XLVIra.
Aristotle does not explicitly say that this is the cause of the phenomenon, but describes the sleeper’s perception in these cases as weak (see Insomn. 3, 462a20–21, 22, 25). In the medieval tradition, however, the weakness ascribed by Aristotle to the sleeper’s perception is transferred to his sleep; see Christina Thomsen Thörnqvist, “Aristotle and His Early Latin Commentators on Memory and Motion in Sleep,” in Memory and Recollection in the Aristotelian Tradition: Essays on the Reception of Aristotle’s De memoria et reminiscentia, ed. V. Decaix and C. Thomsen Thörnqvist (Turnhout: Brepols, 2021).
Buridan points out that there is no name for the first sub-category of (3): “et huiusmodi apparitiones fiunt etiam aliquando in somno et cum fiunt in vigilia non dicuntur somnia, quia deficit connotatum per hoc nomen somnium, sed quando fiunt in somno, tunc dicuntur somnia.” (John Buridan, Quaest. Somn.Vig., fol. XLVIra.)
A similar list covering only (1)–(3) is found in Walter Burley, Exp. Somn.Vig., 501.18–502.10.
“Fantasia enim reservat species sensibiles sine certa differentia temporis sed memoria reservat species et intentionem sensibilium cum certa differentia temporis. Ideo per fantasiam res apparent nobis ac si sint praesentes, sed per memoriam res apparent nobis quod tunc vidimus tales res vel audivimus etc.” (John Buridan, Quaest. Somn.Vig., fol. XLVIrb.)
Buridan’s description of the formation of dreams in qu. 24 of his question commentary on de An. 2 seem to be the reason for the conclusion in Peter G. Sobol, “Sensations,” 197, that in Buridan, memories are the “raw material of dreams”; however, as demonstrated above, it is evident from Buridan’s classification of apparitiones in his commentary on the Parva naturalia that this is not the case; the sensible species stored sine certa differentia temporis in imagination are the raw material of the dream.
“Somnia enim non sunt verae apparitiones, immo falsae, quia apparet praesens quod non est praesens.” (John Buridan, Quaest. Somn.Vig., fol. XLVIrb.) Interestingly enough, Brito, when discussing the role of the intellect in preventing us from being deceived by our dreams, claims that memory also occasionally can make us aware that we are not perceiving but dreaming: “Aliquando intellectus est in actu, quia aliquando somnium est ita terribile quod intellectus iudicat istud esse impossibile accidere, sicut quando aliquis somniat aliquod inhonestum sibi accidere credit se somniare. Etiam aliquando memoria fit in actu, et quando aliquis iudicat de praeterito ipsum esse praesens et memoratur ipsum esse praeteritum, tunc iudicat istud esse somnium, et ita deceptio non latet ipsum.” (Radulphus Brito, Quaest. Somn.Vig., 66.)