1 Introduction
How many senses do we have? The usual answer is five: sight, hearing, smell, taste, and touch. Yet some people try to defend the existence of other senses: for example, the sense of temperature can be considered as an autonomous, additional sense. After all, we do not touch temperatures, or so they would argue. Other people, by contrast, have tried to take the opposite direction, and admit fewer senses: for example, why could smell and taste not be one sense? When your nose is blocked up, you do not perceive the flavour of food anymore, these people would say. If we try to answer these questions, we immediately see that there is an important methodological problem connected with them: we are not clear about the criterion that we should choose in order to distinguish the various senses. We do not even know whether we ought to look for the criterion in the “region” of experience or physiology. One may be tempted to sort out the senses by relying on experience and thus give priority to phenomenology, considering various psychic activities to determine whether one “has the impression” that they belong to the same sense. Or, one might rely on physiology instead and focus either on our sense organs, taking their varieties as a guide to distinguish our senses, or track some relevant brain processes that might provide a list of our sensitive capacities. Agreement on these methodological issues seems to be a prerequisite for discussion of the classification of the senses.
Franz Brentano made a clear choice on this point: he relies on phenomenology. His understanding of phenomenology is broad, as it includes not only the act-pole of our experiences, but also their object-pole; that is, it extends to the entities towards which our mental acts are directed. His criterion for the determination of the number of senses is phenomenological-objectual: the senses are to be classified according to the various kinds of sensible qualities, such as colours and sounds, that appear to us. More precisely, the most general kinds of sensible qualities give us, as their correlates, the various senses. According to Brentano, this must be the guide for the identification of the senses and not physiology. However, pointing toward sensible qualities is not yet enough, as one would in turn need to know what the most general kinds of sensible qualities are. But here again one is in need of a criterion. Brentano has a suggestion: each kind of sensible quality has a specific pair of extremes, such as light vs. dark and high vs. low. This criterion leads him to admit only three senses, namely sight; hearing; and “feeling,” which gathers together smell, taste, and touch. Brentano’s reason for attributing cases of sensation to the same sense is the following: if the aggregation of one sensible quality with another has an impact on the estimation of the position of these sensible qualities on the scale of their opposites, then both sensations belong to the same sense. Interestingly, Brentano thus presents a casuistic of sensation aggregation to determine if two sensations belong to one or distinct genera.
Did the reader notice anything Aristotelian in the description presented above? Although it has a very modern flavour, as it opposes phenomenology to physiology, the two basic criteria that Brentano uses are in fact ancient. Brentano explicitly borrows from Aristotle both the thesis that senses must be distinguished according to kinds of sensible qualities and the idea that the specificity of the extremes allows us to sort out the most general kinds of sensible qualities (for discussion, see chapter one above). Brentano says that the first of these two criteria is found in and defended by Aristotle, whereas the second is just a hypothesis suggested by Aristotle. In sum, Brentano seems to be both a phenomenologist and an Aristotelian philosopher.
From an historical point of view one would like to compare Brentano’s reading to Aristotle’s texts and see to what extent he is faithful to Aristotle. From a more theoretical point of view, Brentano’s adoption of phenomenological instead of physiological criteria requires some justification: why not sort out sensations by appealing to differences among sense organs? Why not take the brain into consideration? Besides, the view defended by Brentano that there are only three senses is quite unconventional, and so one might need to know more about his argumentation before judging its value. This chapter is meant to tackle these issues. The first section introduces Brentano’s general theoretical approach to psychology. The second section presents in detail his theory of the classification of the senses; this will be the occasion for considering his argumentation against physiology and seeing how he justifies his reduction of the senses to three. In the third section, I will first evaluate Brentano’s reading of Aristotle and then the philosophical significance of the Brentanian position.
2 Brentanian Psychology
Brentano’s major theoretical approach to psychology is presented in his lectures on “descriptive psychology,” also called “descriptive phenomenology,” given in Vienna in 1887–88, 1888–89, and 1890–91.1 These lectures are the starting point of an important methodological stance in the philosophy of mind, namely that of undertaking a first-person analysis of our psychic life. According to Brentano, such a study is possible at all levels of our mental acts: we can provide not only an analysis of our emotions from the first-person point of view, but also detailed descriptions of our sensations, of our imaginary and conceptual presentations, and of our judgements. Descriptive psychology identifies the basic elements of our psychic life, analyses their nature, and shows how they combine from a logical-ontological point of view. Brentano opposes “descriptive psychology” to “genetic psychology.” The latter includes psychophysiology and studies the causal relations responsible for the appearance and disappearance of our mental acts. Physiological inquiries in psychology, for Brentano, are far from illegitimate. However, he takes descriptive psychology to be a prerequisite of any such genetic, causal research. Brentano’s basic argument is that it is a prerequisite for an adequate study of the genesis of a set of entities that they first be identified and analysed. One example he gives regards “error and delusion” (Irrtum und Wahn): if one does not have a good account of the differences between a correct and an incorrect judgement, one will fail to explain the genesis of error and delusion, since one will be unable to identify the causal chains responsible for the presence or absence of the determining elements of these phenomena.2
Descriptive psychology must be done from the first-person point of view. Thus, even in domains in which psychophysical causality plays an important role, it should not, in Brentano’s view, enter into the psychological description. Notably, when Brentano tries to determine what features are proper to sensation, he focuses exclusively on phenomenological aspects. In his view, sensations are, roughly speaking, intuitions of real sensible qualities.3 Any mental act which presents itself to inner consciousness as such an intuition is a sensation. This leads Brentano to hold that so-called “objective sensations” and hallucinations belong to one and the same class of psychic phenomena. As a matter of fact, they are phenomenologically equivalent and one has to refer to a causal story in order to explain how they differ. The causal story indeed involves physiological elements, but it does not affect their structure from a phenomenological point of view.4
Brentano has a broad understanding of the scope of descriptive psychology. This discipline analyses our “phenomena.” Among them Brentano distinguishes psychic and physical phenomena. Inner consciousness is turned toward psychic phenomena, such as sensations, conceptual presentations, and so on. However, it also grasps physical phenomena to some extent. “Physical phenomena” is another name for sensible qualities, including colours, sounds, and flavours. In his lectures on descriptive psychology, Brentano holds that every mental act has an intentional relation to a so-called “immanent object.” The mental act is thus relational and has an object as its correlate. From an ontological point of view, there is a major difference between these two relata: the mental act is real, whereas the intentional correlate is unreal.5 These are technical terms and require a brief explanation. In Brentano, realia are causally active and acted-upon entities, whereas irrealia are causally inert and cannot be acted upon; realia have their own coming-to-be and ceasing-to-be, whereas irrealia come to be and cease to be together with realia. Among irrealia, Brentano counts various entities, including not only immanent objects, but also past and future things, abstracta, states of affairs, collectives, and so on.6 When a mental act, which is something real, appears, its unreal sequel, namely an immanent object, also comes to be.
Brentano’s thesis is that inner consciousness grasps not only psychic phenomena, but also their corresponding immanent objects. In other words, inner consciousness has access to two kinds of things: real mental acts and their unreal correlates.7 From the point of view of outer perception (äussere Wahrnehmung), that is, the perception of the external world, colours, sounds, flavours, and the like appear as real; however, from the point of view of inner perception, that is, of self-consciousness, they are grasped as something unreal, namely as immanent objects:8
Inner experience shows us no colours, no sounds, etc., as existing in reality. But it shows us a sensation of colours, etc. and thus these as immanent objects of our sensations, as phenomena. As such, they belong to the content of sensations and their description falls to descriptive psychology.9
In a similar manner, Brentano says the following:
One is telling the truth if one says that phenomena are objects of inner perception, even though the term “inner” is actually superfluous. All phenomena are to be called inner because they all belong to one reality, be it as constituents or as correlates.10
This is an important point, as it shows that, for Brentano, descriptive psychology, or “descriptive phenomenology,” as he also calls it, is not restricted to the analysis of psychic phenomena, but also analyses physical phenomena to the extent that they are immanent objects. In other words, Brentano admits not only an act-, but also an object-phenomenology.11 From this starting point, he takes up the description of the many features that these physical phenomena exhibit: for example, colours always appear extended, they are either pure or mixed, and so forth.12 Note that, from a metaphysical point of view, Brentano thinks that reality lacks secondary qualities: defending a rather standard modern view, his picture of the physical world is that of the physicists and, thus, contains exclusively the items that they admit: atoms, waves, etc.13 Such physical items do indeed act on our sense organs, and they cause acts of sensation; these acts, in turn, are accompanied by their respective correlates, for example, colours or sounds, which, however, do not exist in the external world.
In brief, secondary qualities such as colours, sounds, and flavours, which are “physical phenomena,” appear as real to outer perception but do not exist as real. By contrast, they appear as unreal to inner perception, and do exist as unreal.14 As such, they have many features that can be studied. The science to which their study falls to is “descriptive psychology,” or “descriptive phenomenology,” which is thus revealed as a first-person analysis of our mental acts and their objects.15 This point will be important for the understanding of Brentano’s views on the classification of the senses, as he will use mostly object-phenomenology to sort out the various senses.
3 Brentano’s Account of the Classification of the Senses
Brentano’s account of the classification of the senses is intended to be Aristotelian, as in fact is the case with many other elements in his thought: in addition to being a phenomenologist, Brentano is an Aristotelian philosopher. He started his philosophical training by working on Aristotle, and he wrote his doctoral dissertation on the different senses of ‘being’ in Aristotle (Von der mannigfachen Bedeutung des Seienden nach Aristoteles16 ), under the supervision of Friedrich Adolf Trendelenburg, who was himself deeply involved in Aristotelianism.17 Moreover, Brentano’s Habilitation is on Aristotle’s psychology (Die Psychologie des Aristoteles).18 Yet Brentano was not just a commentator on Aristotle, but rather, as indicated, an Aristotelian thinker. He held that in his time, which was dominated by German idealism, he had to find some new starting point for philosophy. Aristotle, read with the help of Thomas Aquinas, provided this starting point:
As an apprentice, I had first to join a master and, since I was born in a period of most appalling decay in philosophy, I could find no one better than old Aristotle, for the understanding of whom – which is not always easy – Thomas Aquinas often had to help me.19
It must be recalled that Brentano was a priest and abandoned the priesthood after having rejected papal infallibility.20 Despite this abandonment, the Aristotelian-Scholastic influence remained quite strong in his thought, and in particular in his psychology. Just to give one important example, when Brentano introduces his intentionality thesis – namely that psychic phenomena are characterised by their being directed toward an immanent object – he mentions Aristotle as the source of the thesis (more precisely, he mentions certain passages of the De anima on the presence of the sensible as sensible and the intelligible as intelligible in the soul).21 Yet Brentano also affirms there that he is inspired by the scholastics’ claim that the objects of thought exist in the mind “intentionally,” and one medieval author that he quotes in that context is Aquinas.22
In his inquiries in psychology, Brentano devoted many discussions to sensation, especially in his Untersuchungen zur Sinnespsychologie.23 In that context, one of the topics that interested him was that of the classification of the senses. As indicated, his answer on the issue is explicitly based on Aristotelian material. For Brentano, senses are classified according to the varieties of their objects, that is, according to the most general distinctions found among sensible qualities. This is an Aristotelian move:
So, what is the true principle of the classification of the senses? Aristotle said that the senses are to be distinguished on the basis of the genera of the sensible qualities, and because these, for example, sight- and hearing-impressions, are different – there colour, here sound – we are dealing with two senses, not one.24
Recall that since Brentano does not admit secondary qualities in his metaphysics, he uses a merely phenomenological criterion here: from the point of view of descriptive psychology, we notice a certain diversity among the physical phenomena that appear to us as objects of sensation. This diversity in our object-phenomenology should guide us in the classification of the senses.25 Brentano does not mention his textual sources in Aristotle, but he is probably thinking here of two passages from the De anima. The first is about the methodological issue of knowing what psychology should begin its study with. Aristotle claims that there is a definitional priority of the acts with respect to the psychic faculties, and of the objects (or, more precisely, the “opposites” of the acts, as Aristotle does not literally talk of “objects”) with respect to the acts, so that the objects should be the starting point of the investigation:
It is necessary for anyone who is going to conduct an inquiry into these things to grasp what each of them is, and then to investigate in the same way things closest to them as well as other features. And if one ought to say what each of these is, for example, what the intellective or perceptual or nutritive faculty is, then one should first say what reasoning is and what perceiving is, since actualities and actions are prior in account to potentialities. But if this is so, and their corresponding objects are prior to them, it would for the same reason be necessary to make some determinations about, for instance, nourishment and the objects of perception and reasoning.26
The second passage applies this methodological position to the inquiries on sensations, stating that:
Among things perceived in their own right, exclusive objects are properly perceptible objects; and it is to these that the essence of each sense is naturally relative.27
Aristotle’s basic idea is that the understanding of the various faculties of the soul requires the understanding of what their acts are; for example, knowing what the faculty of sight is requires knowing what happens when it is activated, that is, knowing what it is to see. Furthermore, describing the activity of seeing requires mentioning colours, as sight can be aptly described as the sensation of colours. At any rate, this is apparently the way Brentano understands Aristotle: he attributes to him the view that various impressions are distinguished on the basis of their being about such and such a sensible quality.
One may wonder why Brentano does not use physiological criteria. What would be the problem if one were to take the various perceptual peripheral organs (eyes, ears, etc.), and hold that there is one unique sense corresponding to each of them? One could then say that sight is the psychic activity that is produced by the stimulation of the eye, hearing by that of the ears, and so on. In Brentanian terms, the concern would thus be over why genetic psychology cannot provide us with the right number of senses and why we have to rely on descriptions from the first-person point of view. Brentano answers by referring to an experimental hypothesis which involves not only peripheral organs, but also the connections between them and the brain. According to Brentano, if you stimulate a specific peripheral organ, for example the eyes, but you connect the nerves of this organ to those of another organ, for example those of hearing, so that the latter nerves bring the external stimulus to the brain, not the former, you will not have a sensation of sight anymore, but of hearing:
And also the reference to distinct external organs cannot be decisive for heterogeneity. We know that if the nerves of the eye were connected with the nerves of another sense, for example of hearing, an excitation of the eye would result in a sound quality, whereas the appearance of colour would vanish.28
The problem would thus be that you would hear a sound due to a stimulation of your eye; yet according to the physiological criterion mentioned above, you would have to admit that this sensation is one of seeing – a strange conclusion, to say the least. Thus, Brentano rejects the classification of the senses that results from focusing on sense organs and sticks to his Aristotelian account, which favours sensible qualities.
However, once this has been established, the difficulties are not over: one would like to know something else, namely, how to distinguish the genera of sensible qualities. The question is indeed of primary importance, since only its answer can give us the correct number of senses. We have the intuition that some sensible qualities belong to different genera, for example colours and sounds, but what justifies us in believing this? Is there a primitive distinction given when one experiences these qualities? Is there something more to say about the distinction? Brentano, in his first lectures in descriptive psychology (from 1887–88), mentions a hypothesis in which physiology plays the distinguishing role. He finds this hypothesis in John Locke. Brentano says that Locke, in contrast to Aristotle, does not think that sensible qualities have intrinsic features that divide them into genera. Rather, for Locke, qualities are grouped into genera according to their being received by this or that peripheral organ, colours by the eyes, sounds by the ears, and so on:
[Locke] wanted to see no greater kinship between red and blue than between red and the note c in the scale. If we gathered the former together and distinguished the latter, it is only because they have been conveyed to us via different organs (eyes and ears). And according to him, “colour,” “sound,” means the following: “content of sensation exclusively received through the eye (ear).”29
Brentano is apparently referring to the following passage in Locke’s Essay: “For when white, red, and yellow are all comprehended under the genus or name colour, it signifies no more but such ideas as are produced in the mind only by the sight, and have entrance only through the eyes.”30 What is wrong with this view? Although Brentano does not immediately tackle the issue, and thus does not directly answer Locke, he explains later in the text why such a position is problematic. He wonders whether it would be a good move to conclude from the existence of distinct nerves for smell and taste to a distinction of the sensible qualities of odour and flavour.31 His answer is negative and is based on a variant – as it is applied to sensible qualities – of the argument mentioned above concerning the classification of the senses. Brentano holds the following:
Let us think of a nerve fibre of the eye connected with a nerve fibre of the ear in such a way that the central part belongs to the nerve of hearing, and the peripheral one to the one of sight; through the light that would excite the retina a sensation of sound would emerge; the same end structure which now serves to the awakening of a colour impression would serve to the awakening of a sound impression.32
The problem here is that the stimulated peripheral organ would be the eye, so that you would have to conclude that the sensible quality emerging from its stimulation is a colour; however, what appears seems rather to be a sound. Interestingly, Brentano adds in this case that he is offering a pure hypothesis, as such crossing among nerves has never been experimentally tested. He adds, however, that we all know cases which show that the physiological criterion is inadequate. For example, the feeling of being dazzled by light emerges from a stimulation of the eyes via light waves, but this does not make dazzlement a colour.33 Thus, physiological arguments referring to peripheral organs are unable to solve the problem of the identification of the highest genera of sensible qualities.
We are therefore back to the question of how to distinguish the genera of sensible qualities. Brentano refers to Aristotle, who hypothesises that each kind of sensible quality, except touch, has one peculiar opposition of extremes: “Aristotle claimed that there are in each qualitative genus two extremes, as, for example, black and white for colours, [and] an extreme of high and low for sounds.”34 The passage Brentano has in mind surely is the following:
Every sense seems to be of a single pair of contraries: sight of white and black; hearing of high and low; taste of bitter and sweet. But among the objects of touch are included many pairs of contraries: hot and cold, dry and wet, hard and soft, and whatever else is of this sort.35
Yet immediately after having said this, Aristotle asserts that “in the case of the other senses there are also several pairs of opposites.” He mentions “spoken sound,” which has “loudness and softness, and smoothness and roughness of voice,” and claims that something similar holds for colour. However, he also seems to suggest that these pairs of opposites are still “subordinated” to sound or colour.36 Now, these claims of Aristotle have led his readers to wonder whether sensible qualities have one or several pairs of opposites, and if they have several, how these exactly relate to each other.
When commenting on Aristotle’s text, Aquinas refers to Metaphysics 10.4, 1055a23–33, in which Aristotle holds that in every genus there is a “complete difference” (
Brentano may have been inspired by the Aquinas-Trendelenburg “first opposition” reading, which qualifies Aristotle’s prima facie problematic claim that senses other than touch also have a plurality of opposites, which goes against the idea that sensible qualities are picked out by one pair of opposites.41 In any case, Brentano sticks to the hypothesis that qualities from one genus are identified thanks to one opposition of extremes.42
Note that for Brentano these divisions are divisions of a genus into species. So, the genus of visual qualities is divided into the species of light and dark qualities. What Brentano calls “coloration” (Kolorit), or “saturation” (Sättigung), is an additional qualitative feature which might accompany light or dark sensible qualities, but need not, and which turns them into red, blue, and so forth, either light or dark. Brentano criticises Aristotle for holding that all colours are simply mixtures of black and white. For Brentano, there are only shades of grey between black and white; colours stricto sensu come about in addition to brightness. It is also true, however, that each shade of colour has a specific lightness or darkness; such shades, thus, seem to be a combination of a species of coloration and a species of brightness. Whereas Brentano’s opposition between light and dark seems to correspond to what in contemporary colour theories is called “brightness,” his concept of “coloration,” synonymous with “saturation,” seems to overlap both the contemporary categories of hue and saturation.43 In addition to coloration and saturation, Brentano also admits an “intensity” (Intensität) for colours that he understands in terms of purity: a blue taken alone is more intense than a blue mixed with another colour. Like visual qualities, audible qualities divide into the species of high and low noises, which may, but need not, be accompanied by the additional, saturated quality of “tone”: c, c#, etc. As for their intensity, it depends on whether they sound alone or in “harmony” (Mehrklang).44
So, for Brentano, genera of sensible qualities are distinguished by a single characteristic pair of opposites. Brentano then makes an additional move, stating that the extremes of the qualities of distinct genera are in a relation of analogy: so lightness for colours and highness for sounds are analogous, and similarly for darkness and lowness.45 Brentano is of course aware of the technical connotation of the term “analogy” in the Aristotelian context, as he himself uses it in his dissertation on the senses of being.46 In the Aristotelian-Scholastic tradition, “analogy” comes in many variants. One of them, which is inherited from Aristotle himself, is the analogy of proportion: a is to b what c is to d.47 Now, Brentano’s faithful pupil Anton Marty holds that “in more recent times” the usual sense of “analogy” is that of proportion.48 So, if Brentano does not further specify what he means by “analogy,” it is then likely that he is thinking of this kind of analogy. His source for the admission of an analogy between the extremes of sensible qualities seems to be Aristotle again, more precisely De sensu 7, 447b21–448a19.49 Brentano, when talking about these analogy issues, says that for Aristotle sweetness is related to bitterness like a light colour to a dark one.50 In the text in question, Aristotle discusses the relations between sensible qualities from distinct genera, like colours and flavours. He explains that these qualities, although distinct with respect to their genus, have some proximity. He does not literally talk of an “analogy” (
As for the explicit reference to analogy, Brentano might again have found it in Aquinas, more precisely in his commentary on the De sensu. Aquinas holds that white and black, on the one hand, and sweet and bitter, on the other hand, are “principles corresponding to each other proportionally” (principia proportionabiliter sibi respondentia). Indeed, every sensible quality is either “a state” and “something perfect” (habitus and aliquid perfectum) or “a privation” and “something imperfect” (privatio and aliquid imperfectum). The white, for example, is a state, and the same holds for the sweet; as for the black and the bitter, they are both privations. According to Aquinas, sensation thus directs itself toward these cross-generic pairs of sensible qualities in the same “mode” (modus), even if they are objects of different senses.53 Aquinas thus glosses the aforementioned text in the following way: “vision senses the white in the same way that taste senses the sweet; and as vision senses the black, so the taste senses the bitter.”54 Aquinas’ use of the notion of “proportion” here might be what led Brentano to talk of an “analogy” – of proportion – between the various extremes of the sensible qualities.55
Thus, extremes like light and dark for colours, high and low for sounds, and so forth are not identical but they are still analogous. This means, Brentano says, that some colours can be described as high, others as low, by analogy; some sounds are light, others dark, by analogy again. Brentano makes a quite broad application of such comparisons. One finds him saying, for example, that sweet is high, whereas bitter is low, by analogy; that the sensation of cold is high, but that of warm is low, again, by analogy; similarly, and by analogy again, the sensation of pressure is high, the one produced when one holds his breath is low; and so on.56
But why is Brentano interested in such broad classification of sensible qualities on a scale of, say, “high” and “low”?57 Brentano wants to show that some aggregations of features which seem to be from distinct genera, for example sweetness and heat, have an effect on the estimation of their respective “highness” or “lowness.” A sweet drink, for example, seems less sweet when heated because the “lowness” of heat leads us to underestimate the “highness” of sweetness. But if this is the case, then they belong to the same genus of sensible qualities. As a matter of fact, the influence of one of them on our estimation of the “highness” or “lowness” of the other shows that they are “high” and “low” in the same manner, which in turn shows that they belong to the same genus, since a genus of sensible qualities is defined by a pair of extremes. In short, only aggregations of qualities of the same genus can affect our estimation of their “highness” or “lowness.” A case that Brentano mentions to illustrate his position is that of the mixture between colours. If you take a given colour and mix some other, lighter one with it, the first colour will seem lighter to you. When you have a similar process between other sensible qualities, it means that they belong to the same genus. This explains why Brentano is interested in the classifications mentioned above. He starts to fix sensible qualities on the scale of “high” and “low,” and once this is done, experiments to discover whether their aggregations have an effect on our estimation of their position on the scale. If this is the case, they are from the same genus of sensible qualities.
Now, the application of this criterion leads him to hold that there are only three genera of sensible qualities and correlatively only three senses: sight, hearing and what he calls “feeling” (Spürsinn).58 Basically, this means that touch, smell, and taste are aspects of the same sense. In order to justify this unusual thesis, Brentano appeals to a series of experiences involving the system of aggregations that I mentioned before.
Brentano’s idea, I repeat, is that if the aggregation of one sensible quality with another provokes a modification of the estimation of the degree of the other, then both sensible qualities are “high” and “low” in the same manner; and if they are “high” and “low” in the same manner, then they belong to the same genus of sensible quality, since the distinction among pairs of extremes is the criterion for the distinction of the genera of sensible qualities. Here is Brentano’s argument:
What, thus, appears, by contrast to what we presumed, is that sensations of touch and of temperature are of one genus. This is revealed by the fact that the simultaneous sensation of temperature has an influence on the estimation of the size of the pressure. If one warms a thaler and puts another cooled one on the hand, the second one appears significantly heavier. This has its reason in the fact that the sensation of pressure belongs to the clear ones like the sensation of cold. What happens here is similar to the cases in which the admixture of clear colours or sounds makes us estimate a colour or sound as clearer (higher), whereas the addition of a darker sensation in the same sense leads to the underestimation of the clarity. Something similar happens if warm and cold sweet water is tasted in turn: the cold water appears sweeter, the hot water less sweet. And the same also holds for the salty and the sour, whereas with coffee, which is bitter, the cold peculiarly modifies the taste, so that it tastes more sour than bitter. The bitterness is clarified through the cold. If one follows this, one reaches this result: the sense for colours and also the sense for sounds are each to be distinguished as a particular one. But all the so-called “inferior” senses are a single sense.59
Brentano argues in this text that, first, sensations of temperature do not form a proper genus of sensation, but belong to one genus with touch. His argument for this is the one mentioned before, namely that the aggregation of “high” and “low” sensations of temperature and touch have an influence on the estimation of their highness or lowness. Then, in a second step, Brentano shows that aggregations between sensations of temperature and sensations of taste interact in the same way: as said above, given that sweet is “high” and warm is “low,” warming sweet drinks make them appear less sweet, that is, less “high.” Thus, these facts not only show that sensations of temperature and touch fall under the same genus, but also that taste must be included in this genus.
Note that Brentano is apparently talking of our estimation of the qualities: for example, he does not say that the drinks are less sweet, but that they are taken to be less sweet. So, Brentano, who, I repeat, is not a realist about secondary qualities, seems to admit two levels of phenomenality in sensation. At a first, basic level, one experiences properties such as sweetness, hotness, and so on, that are purely phenomenal in the sense that their being depends on their being perceived. The co-presence of some of these qualities together might, however, create, at a second level, an impression of these properties which differs from their tenor at the first level. In a similar manner, Brentano does not claim that a colour to which a lighter one is added becomes lighter, but that it appears lighter. The case of colours might help to better understand the idea of two levels of phenomenality. In Brentano’s theory, colour mixtures are explained in terms of a juxtaposition of small points of pure colours on a sort of chessboard; a mixture never alters a pure colour. Thus, what Brentano seems to mean, in the case mentioned above, is that if you admix another, lighter colour to a blue shade a the result will appear to be a colour lighter than blue shade a, but darker than the added colour, although what you have is a chessboard made up of blue shade a and the added colour.60 Another text makes it clear that the discussion is about our estimation of sensible qualities: Brentano holds that if you put your hands in two buckets, one with hot water and one with cold water, and move your hands, the cold water will seem heavier. This is due to the fact that pressure is “high,” whereas warmth is “low,” which leads one to underestimate the resistance of the hot water.61 Now, Brentano talks of this as an “illusion” (Täuschung); someone who was non-sensitive to temperatures would take both resistances to be the same.
I have not found a similar example in Brentano for taste and smell, that is, a case of an influence on the estimation of “highness” and “lowness” due to aggregations of qualities of taste and smell. However, it is clear that he defends the thesis that taste and smell fall under the same genus of sensation. He gives two other sorts of argument in favour of this point. First, he appeals to an authority, by quoting the De sensu again, where Aristotle says that taste and smell are “almost the same affection” (
Without expressing himself as generally [as Aristotle], the common man, however, gives proofs of this in specific cases. He states that flavour and odour have kinship in many sorts of food, for example in vinegar. Still more striking are statements in which the taste of something is characterised through its similarity with that of something else which has never been savoured otherwise than with the nose. For example: “it tastes like mouse droppings.” Or as a woman told me recently: snails taste like swamp.63
Thus, based on this argument, Brentano puts together odours and flavours. And, since sensible qualities of taste have a common genus with those of touch, smell, taste, and touch form one genus of sensation, that of feeling (Spürsinn). To my knowledge, Brentano does not label the pairs of opposites of the sense of feeling, that is, he does not give names to the poles which are analogous to lightness and darkness, on the one hand, and highness and lowness, on the other hand.64 He holds that saturation is found in an analogous way among sensible qualities of the sense of feeling: mere touch sensations and coldness are unsaturated, by analogy to greys or noises, whereas sensations of hotness as well as odours and tastes are saturated.65 These qualities also have intensity: for example, pain – which Brentano indeed counts as a sensible quality66 – is more intense than warmth.67 Independently of these questions, it is clear that sensible qualities of taste, smell, and touch form a common genus, so that they are correlated to one unique sense. Brentano’s final word about the classification of the senses is thus the following: there are all in all three senses, namely sight, hearing, and feeling.
4 Evaluation
I would like to close this paper with both an historical and a systematic evaluation of Brentano’s account. That is, I want to ask, first, if his account is truly Aristotelian and, second, to what extent the account is defensible.
4.1 Historical
Brentano, when claiming that there are as many senses as there are genera of sensible qualities, means to follow the De anima. He seems indeed to be in line with Aristotle, who holds that the faculties of the soul are defined via the acts, and the acts, in turn, via the objects. However, Brentano reaches the conclusion that there are only three senses, whereas Aristotle admits five. Why this discrepancy?
As indicated, Brentano’s distinction is meant to be phenomenological, as he does not believe in the existence of secondary qualities in the external world. According to him, as we have seen, sensible qualities can only be found in the mind, as intentional objects. He also holds that such qualities are “unreal” entities. With this technical term, he means items which exist, but have no causal efficacy at all, by contrast to realia, which both exist and can cause some effect. This is indeed very different from what Aristotle thinks. In Aristotle, sensible qualities are not merely mental; they do exist independently of us, and they are objectively divided into five genera. Our sensation, in turn, is perfect because it has five different senses each “capable of receiving” (
To be sure, the relation between phenomenology and causality in Aristotle’s theory of sensation is not easy to determine. In recent years, Aristotle scholarship on this issue has been dominated by a complex debate between Burnyeat and Sorabji on the specific nature of the causal relation in Aristotle’s account of sensation.71 Roughly speaking, Burnyeat’s interpretation of Aristotelian sensitive causality treats it as merely phenomenological: the effect of the object is nothing other than the “awareness” of the object. By contrast, Sorabji, relying on, among other passages, De anima 2.12, 424b16–17, distinguishes the awareness of the object from the object’s causal action explained in physiological terms (for example, in vision, the causal action is the colouring of the eye-jelly). Note that Burnyeat and Sorabji, although they explain causality differently, both think that the sensible qualities in Aristotle’s psychology have a causal effect. In one case, they produce awareness, in the other case, a physiological change.
Brentano himself is a protagonist in the debate since both Burnyeat and Sorabji take him to defend the phenomenological reading in his 1862 book on Aristotle’s psychology. According to this reading, the effect of the object is the awareness of it. Yet, Brentano will take a different stance in his later works. Indeed, in his Psychologie, when commenting on a passage from the De anima on psychic causality (namely 3.2, 425b26–426a26), he criticises Aristotle for assimilating intentionality and causality, as the (intentional) correlation between hearing and its object, namely sound, is not a causal one: “[…] classifying the pair of concepts, hearing and sound, under action and passion is completely mistaken.”72 Thus, although Brentano might have been a defender of the phenomenological reading of Aristotle, he clearly became an opponent of the assimilation of intentionality and causality. In his later works, he strictly takes apart these two aspects of mental acts. As indicated above, he even thinks that the study of intentionality and psychophysical causality are devoted to two different disciplines, namely descriptive psychology (or “descriptive phenomenology”) vs. genetic psychology. This distinction is fully absent from Aristotle’s psychology.
The purely phenomenological stance taken by Brentano in his account of sensation, compared to Aristotle’s focus on causality, might explain why they arrive at different results, namely Aristotle’s five and Brentano’s three senses, even though their criterion for the classification of the senses seems to be the same – namely the differences among genera of sensible qualities. As a matter of fact, Brentano is treating the sensible qualities phenomenologically. They are merely found in the mind, as correlates of our acts of sensation; in Brentano’s jargon, they are irrealia, that is, entities which exist, but are causally inert. By contrast, Aristotle takes sensible qualities to exist in the physical world as causal agents of sensation. For this reason, he does not follow (or at least does not follow only) first-person experience, but takes into account some physical reasons that lead to further distinctions among sensible qualities.73 In the case of taste and smell, when Aristotle holds that they are “almost the same affection,” it is probably not so much for phenomenological reasons – based on, for example, the experiences attributed by Brentano to ordinary people – as for physical reasons: odour and flavour both involve a constitutive relation to a dry element, a so-called “flavoured dryness” (
Note that, independently of the contrast between phenomenological vs. non-phenomenological inquiries, Aristotle could have reduced the senses to three. Indeed, with respect to taste and smell, he holds, as indicated above, that they are “almost the same affection.” Moreover, he claims that odours receive their names from similar flavours.75 Aristotle also has a problem with touch because it seems to have not just one object but rather (at least) two. Sometimes, he seems to identify touch not so much via its objects as via the fact that this sense always implies a direct contact with its objects.76 However, this also leads him to hold that taste is like touch77 although he does not seem to assimilate them in the final analysis: as Sorabji insists, Aristotle treats them separately in the De anima.78 Yet if taste and smell are assimilated, and if taste is a sort of touch, there seem to be tendencies (or at least reasons) in Aristotle’s philosophy for reducing the number of senses to three, like Brentano does.
4.2 Systematic
In this (last) section, I would like to discuss from a systematic point of view some aspects of Brentano’s account of the classification of the senses. First, I will try to figure out what theoretical grounds Brentano might have for choosing his criterion for the distinction of the genera of sensible qualities, which is a central element of his account. Second, I will tackle a series of objections against his views, which, among other things, will lead me to discuss his opposition to the use of physiology in the classification of the senses.
What is Brentano’s justification for defending the idea that sensible qualities are to be distinguished on the basis of the variation of their extremes? The answer to this question is not easy to determine. Brentano may be influenced by the argument given by Aquinas that every genus has a first contrary, namely its highest specific difference.79 This seems indeed to make it possible to identify various genera of sensible qualities, as it allows you to exclude that some sensible qualities are in a relation of genus to species. Take, for example, colours and sounds: the first have light and dark as opposites and the second high and low. In other words, they are both divided into two opposite species. Yet colours and sounds are both sensible qualities. Now, what guarantees that sound does not form a species of colour which in turn divides into high and low, or vice-versa? The answer is the following: neither high nor low contain light or dark as a “mark,” nor vice-versa. This would be one way to arrive at Brentano’s criterion.
However, Brentano may have taken another path, one that begins from experience. Perhaps he noticed the following: one finds in one’s experience sensible qualities that exhibit some highness or lowness in a strict or analogous sense. Some aggregations between these sensible qualities have an influence on the estimation of their place on the “highness” and “lowness” scale, which seems to indicate that they are “high” and “low” in the same sense and, thus, that they belong together. By contrast, sensible qualities of distinct genera do not produce a similar effect on their respective evaluation: sounds do not make colours seem lighter, nor do colours give the impression that sounds are higher. The same also holds of colours and sounds with respect to objects of taste, smell, and touch, which all three seem “high” and “low” in the same sense, as shown by similar aggregation effects. This would be the phenomenological path towards the criterion.
One might raise many objections to Brentano’s theory. First, a general objection, which is often mentioned against first-person psychological inquiries, would be to say that one does not have the same impressions as those described by Brentano. What if I were to claim that the relations of analogies, for me, are inverted: high sounds are related to low ones as dark colours to light ones? Or, to take an example with an aggregation, what if cold water does not seem more resistant to me than hot water?80 Brentano is quite accustomed to such objections, and his basic argument is that descriptive psychology requires training to improve our capacity to notice things which are present in our experience.81 For the above-mentioned analogies, if I were to put you in front of a piano, play one of the lowest tunes and ask you whether it is more similar to black or white, you would surely answer “black” and thus notice what Brentano wants you to notice in your experience. However, some cases seem harder to defend in a similar manner: how long should I practice in order to notice that pressure is a “high” sensation and thus analogous to coldness? Yet Brentano is usually not dogmatic, nor, on the other hand, does he want to shock the common sense view. Rather, he seemingly observed that the aggregations of qualities which are at first sight distinct appear to have an influence on our estimations of these qualities, and this led him to conclude that the qualities in question must belong to the same genus. Even if one is not convinced by Brentano’s restriction of the senses to three, there is at least one interesting point that must be granted: Brentano has a unitary and economical explanation for many phenomena of mutual influence between sensible qualities, such as those between temperature and taste or temperature and weight.
With respect to this last point, one could raise another objection to Brentano, namely that he is not talking of a “mutual influence between sensible qualities,” but merely about misrepresentations: he does not say that the aggregations of qualities modify these qualities themselves, but rather that it has an influence on our estimation of their “highness” and “lowness,” and even talks of these estimations in terms of illusions. So, all this apparently concerns mistakes that we make when grasping these qualities, and says nothing about their intimate nature – telling us neither whether they are, nor whether they are of one and the same genus. Brentano’s assumption here is that the misrepresentation is only possible when the qualities are “high” and “low” in the same sense and, thus, belong to the same genus. As a matter of fact, similar misrepresentations do not happen between colours and sounds. Perhaps one might say that the world appears darker when hearing a sad song; however, this does not literally mean that one experiences the decreasing of light or a dimming of colours, but rather that one has negative emotions directed towards the world (nostalgia, pessimism, etc.).82 In sum, generic sameness is revealed as that which allows for the misrepresentation.83
Finally, the phenomenological stance taken by Brentano might produce some scepticism due to its opposition to physiology. Brentano strongly insists on the fact that physiology is not relevant for the classification of the senses. However, he mainly focuses on the peripheral organs, by claiming that they cannot be decisive. He supports this claim with the argument, discussed above, that one of the sense organs could be connected to the usual path of another one, so that the stimulation of the former organ would create a sensation like those usually produced by the latter organ. One might object that even if Brentano’s arguments about the peripheral organs were sound, it would be less easy to reject a physiological explanation involving the brain. Imagine a study of the brain in which one identified the part devoted to sensation and show that it is in turn divided into n basic parts. One could argue that each of these basic parts is devoted to a basic process of sensation: sight, hearing, and so forth. The identification of such parts would thus answer the question of the classification of the senses.
There is a Brentanian answer to this challenge, although it must be transposed from another, slightly different context. In his 1887–88 lectures on descriptive psychology, in a discussion on the number of pure colours, Brentano invokes Ewald Hering, who seems to admit that one could analyse the brain in order to find out how many pure colours there are. According to this hypothesis, if one finds the right number of “fundamental processes” (Grundprozesse) which are required for vision, one will have the number of “fundamental sensations” (Grundempfindungen) of vision, to which corresponds the range of pure colours.84 Brentano rejects this view for many reasons. Among others, he offers the argument that the number of fundamental physiological processes of vision could be higher or smaller than the number of fundamental sensations; he sees no logical necessity in these numbers being the same.85 It seems to me that his position could be applied to the more general issue of the classification of the senses. If someone wants to defend the view that the discovery of the basic brain processes for sensation would inform us about the number of senses, Brentano would simply answer that the number of basic brain processes might be larger or smaller than that of the basic sense experiences.
Another argument for Brentano’s view could be based on the primacy of descriptive psychology over genetic psychology. Brentano might say that the question of knowing whether some basic neurological elements provide us with a generic distinction among the senses is already determined by what we will accept as genera of sensation in our first-person inquiries. Imagine if we were to find that one basic element in the brain is responsible for seeing red, and another one for seeing blue; we would most probably hold that these elements, although basic from a neurological point of view, are not responsible for a generic distinction among sensations. It is only if we find basic elements which correspond to our first-person distinctions among genera of sensations that we will take these elements to be responsible for a generic distinction. But this means that we are tracking the causes of distinctions that are already established at the phenomenological level.
5 Conclusion
Brentano’s account of the classification of the senses is strongly influenced by Aristotle. First, he identifies the senses by reference to the different genera of their objects, and he takes this to be an Aristotelian move. Second, he classifies the genera of objects themselves following an Aristotelian criterion, by holding that every genus of sensible quality has a specific pair of opposites. Possibly influenced by Aquinas, he adds that the pairs of opposites are analogous to one another. In other words, sensible qualities are all high and low in a strict or analogous sense. When starting to sort out the various senses according to his criterion, Brentano reaches the conclusion that there are only three senses, namely sight, hearing, and feeling. In order to prove this, he mentions a series of experiences in which sensible qualities of taste, smell and touch interact with each other in such a way that the aggregation of these qualities leads to a modification of the estimation of their position on the scale of “highness” and “lowness,” which implies that they are “high” and “low” in the same sense and, thus, that they form one genus.
Since Brentano is not a realist concerning secondary qualities, the objects of sensation he is appealing to are phenomenological. Besides, he rejects explanations in terms of physiological processes both for classifying the senses and for identifying the various genera of sensible qualities. Finally, the experiences he mentions for the fixation of the number of genera of sensible qualities are also based on phenomenology. Thus, at all levels of his theory Brentano uses phenomenological material, or proceeds by what he calls “descriptive psychology,” as opposed to genetic psychology, which includes psychophysiology.
Although some aspects of Brentano’s account are incompatible with Aristotle’s theory, notably with respect to the status of sensible qualities, which for Aristotle are in the external world and not merely mental, it is clear that Brentano manages to borrow and develop many Aristotelian ideas. In the final analysis, he can be described as an Aristotelian-inspired phenomenologist: his account of the classification of the senses contains Aristotelian theoretical insights, namely that of identifying the senses by reference to their objects and that of picking out the genera of objects themselves following pairs of opposites, but they are developed in accordance with a phenomenological sensitivity, that is, from a first-person point of view and by bracketing the psychophysical realm.
Acknowledgements
Drafts of this paper were presented in 2018 at an internal workshop of the research project Representation and Reality: Historical and Contemporary Perspectives on the Aristotelian Tradition at the University of Gothenburg and at the conference Revision and Perversion of Aristotelian Psychology at the Warburg Institute. I thank the participants for their remarks, especially Börje Bydén, Sten Ebbesen, Jakob Leth Fink, Alexander Greenberg, Pavel Gregoric, Rotraud Hansberger, Katerina Ierodiakonou, and Robert Roreitner. I am also very grateful to Juhana Toivanen for his written remarks on the first draft of the paper. Finally, I thank Jordan Lavender for having corrected my English and for having made very useful suggestions of clarification of the text.
Guillaume Fréchette and I are preparing an edition of Brentano’s three lectures series. Brentano’s Deskriptive Psychologie, ed. W. Baumgartner and R. M. Chisholm (Hamburg: Meiner, 1982) contains large parts of the 1890–91 lectures. In the present chapter, I will quote also the lectures from 1887–88, ms. Ps 76, from our forthcoming edition (I am grateful to Thomas Binder for preparing a transcription of the original manuscript for our use).
Brentano, Deskriptive Psychologie, 9 (trans. Müller, 11).
Brentano, Deskriptive Psychologie, 139–40. Brentano adds that sensations are “fundamental,” that is, they do not depend on other mental acts, by contrast, e.g., to emotions, which presuppose a presentation of their object.
Brentano, Deskriptive Psychologie, 136. For a more precise discussion of the relations between phenomenology and psychophysics in Brentano’s philosophy, see the evaluative section below (including the historical part, where his views are contrasted with those of Aristotle).
Brentano, Deskriptive Psychologie, 21.
Brentano, “Abstraktion und Relation,” ed. G. Fréchette, in Themes from Brentano, ed. D. Fisette and G. Fréchette (Amsterdam: Rodopi, 2013), 466–67; Arkadiusz Chrudzimski, Die Ontologie Franz Brentanos (Dordrecht: Kluwer, 2004), 123–75, and 201.
Brentano, Deskriptive Psychologie, 129. I follow here the classical interpretation of Brentano’s theory of the immanent object. For an alternative reading, where the immanent object is not an unreal entity, see Werner Sauer, “Die Einheit der Intentionalitätskonzeption bei Brentano,” Grazer Philosophische Studien 73 (2006): 1–26; and Mauro Antonelli, “Franz Brentano et l’‘inexistence intentionnelle’,” Philosophiques 36:2 (2009): 467–87.
On the fact that Brentano, in his theory of intentionality, admits two different points of view on the immanent object, seen in turn as real or unreal, see Arkadiusz Chrudzimski, Intentionalitätstheorie beim frühen Brentano (Dordrecht: Kluwer, 2001), 104–5.
“Die innere Erfahrung zeigt uns nicht Farben, nicht Töne usw. als in Wirklichkeit bestehende. Sie zeigt uns aber eine Empfindung von Farben usw. und somit diese als immanente Gegenstände unserer Empfindungen: als Phänomene. Als solche gehören sie zum Inhalt der Empfindungen und ihre Beschreibung wird Aufgabe der deskriptiven Psychologie.” (Brentano, Descriptive Psychology (1887/88) [ms. Ps 76], ed. G. Fréchette and H. Taieb, transcribed by Th. Binder (Cham: Springer, forthcoming): n°58012–13; all references to this work are to manuscript pages.)
“Wenn man sagt, Phänomene seien Gegenstände der inneren Wahrnehmung, so sagt man die Wahrheit, obwohl das ‘innere’ eigentlich überflüssig ist. Alle Phänomene sind innere zu nennen, weil sie alle zu einer Realität gehören, sei es als Bestandteile, sei es als Korrelate.” (Brentano, Deskriptive Psychologie, 129 (trans. Müller, 137).) This is a passage from the 1888–89 lectures.
On this distinction, found in Moritz Geiger, a student of Husserl, see Robin D. Rollinger, “Scientific Philosophy: Paul Linke,” The New Yearbook for Phenomenology and Phenomenological Philosophy 5 (2005): 60n14. For an emphasis on the role of the object in Brentano’s theory of sensation in particular, see Olivier Massin, “Brentano on Sensations and Sensory Qualities,” in Routledge Handbook of Franz Brentano and the Brentano School, ed. U. Kriegel (London: Routledge, 2017), 87–96.
Brentano, Deskriptive Psychologie, 14–17, 71–72.
Franz Brentano, Psychologie vom empirischen Standpunkt, vol. 1, ed. O. Kraus (Leipzig: Meiner, 1924/1925), 28; id., Psychology from an Empirical Standpoint, trans. A. C. Rancurello, D. B. Terrell, and L. L. McAlister (London: Routledge, 1995), 14; Tim Crane, “Brentano’s Concept of Intentional Inexistence,” in The Austrian Contribution to Analytic Philosophy, ed. M. Textor (London: Routledge, 2006), 20–35; Massin, “Brentano on Sensations and Sensory Qualities,” 89.
Brentano, at least in Psychologie, 1:28, does not just reject the existence of sensible qualities such as colours and sounds, but also that of the sensible qualities of space and movement, usually included among so-called “primary qualities.” Brentano’s divide between primary and secondary qualities requires further investigation.
Note that Brentano later abandoned his theory of immanent objects; however, he continued to hold that inner consciousness cannot present a thinking subject without presenting an object toward which it is directed (see Brentano, Psychologie, 2:133–38). Moreover, the abandonment of immanent objects did not change his views on the rules to which physical phenomena, although mere appearances, are submitted; for example, he did not begin to defend the view that colours can appear non-extended, nor that they are all pure, etc. (see, e.g., the discussions on the relations between colour and space or on mixed colours in Franz Brentano, Kategorienlehre, ed. A. Kastil (Hamburg: Meiner, 1933), 275 and 81–86).
Franz Brentano, Von der mannigfachen Bedeutung des Seienden nach Aristoteles (Freiburg: Herder, 1862).
On the revival of Aristotle in the nineteenth century, and on Trendelenburg’s role in it, see Denis Thouard, ed., Aristote au XIXe siècle (Villeneuve d’Ascq: Presses universitaires du Septentrion, 2004); Gerald Hartung, Colin G. King, and Christof Rapp, eds., Aristotelian Studies in 19th Century Philosophy (Berlin: De Gruyter, 2019).
Franz Brentano, Die Psychologie des Aristoteles, insbesondere seine Lehre vom ΝΟΥΣ ΠΟΙΗΤΙΚΟΣ (Mainz: F. Kirchheim, 1867). Brentano also wrote two texts on the question of the origin of the soul in Aristotle (Über den Creatianismus des Aristoteles and Aristoteles Lehre vom Ursprung des menschlichen Geistes) and he published a general presentation of Aristotle’s philosophy (Aristoteles und seine Weltanschauung). A posthumous work of Brentano on various themes in Aristotle also appeared (Über Aristoteles).
“Ich hatte mich zunächst als Lehrling an einen Meister anzuschließen und konnte, in einer Zeit kläglichsten Verfalles der Philosophie geboren, keinen besseren als den alten Aristoteles finden, zu dessen nicht immer leichtem Verständnis mir oft Thomas von Aquin dienen mußte” (Franz Brentano, Die Abkehr vom Nichtrealen, ed. F. Mayer-Hillebrand (Bern: Francke, 1952), 291).
For a presentation of Brentano’s life and work, see Denis Fisette and Guillaume Fréchette, “Le legs de Brentano,” in À l’école de Brentano: De Würzbourg à Vienne, ed. D. Fisette and G. Fréchette (Paris: Vrin, 2007), 13–160.
The relevant passages are de An. 2.12, 424a17–24 and 3.8, 431b29–432a1. By the way, Brentano also means to borrow from Aristotle the thesis that mental acts have an unreal entity as correlate. This thesis would come from Metaph. 5.15, 1021a26–b3, where Aristotle claims that some relatives, including the thinkable and the sensible, are not relative by themselves, but because something else, in this case thought and sensation, is relative to them. For an evaluation of the adequacy of this reading of Aristotle, see Hamid Taieb, Relational Intentionality: Brentano and the Aristotelian Tradition (Cham: Springer, 2018), 63–134.
Brentano might here be thinking of Thomas Aquinas, Sentencia libri De anima, ed. R.-A. Gauthier (Rome: Commissio Leonina / Paris: Vrin, 1984), 2.24, and his discussion of esse intentionale. The question of whether Aquinas holds that the items with esse intentionale truly are objects of thought is controversial, as he might rather be a direct realist and hold that our thoughts have reality as their objects; in this case, the items with esse intentionale would be means of grasping reality, but not themselves objects. For more on this, see notably Dominik Perler, Theorien der Intentionalität im Mittelalter, 2nd ed. (Frankfurt am Main: Vittorio Klostermann Verlag, 2002), 80–89.
See notably Franz Brentano, Untersuchungen zur Sinnespsychologie, ed. R. M. Chisholm and R. Fabian, 2nd ed. (Hamburg: Meiner, 1979).
“Welches ist nun das eigentliche Prinzip der Klassification der Sinne? Aristoteles sagte, die Sinne seien nach den Gattungen der Sinnesqualitäten zu scheiden, und weil diese z. B. bei Gesichts- und Gehörseindrücken verschieden seien – dort Farbe, hier Schall – so handle es sich um zwei Sinne, nicht um einen.” (Brentano, Untersuchungen zur Sinnespsychologie, 159.)
The contemporary phrasing of Brentano’s problem is that of the “individuation of the senses,” as underscored by Massin, “Brentano on Sensations and Sensory Qualities,” 92–93; in what follows, I will stick to Brentano’s formulation of “classification of the senses,” but the distinction is merely verbal. Massin’s text, although short, is very helpful, as it mentions many central aspects of Brentano’s theory of the classification of the senses, notably its Aristotelian origins and its non-physiological nature. Aristotle’s position is also discussed in the contemporary literature (see, e.g., Mohan Matthen, “The Individuation of the Senses,” in Oxford Handbook of the Philosophy of Perception, ed. M. Matthen (Oxford: Oxford University Press, 2015), 567–86).
“Auch der Nachweis verschiedener äußerer Organe kann nicht für die Heterogenität entscheidend sein. Wir wissen, daß, wenn die Augennerven mit Nerven eines anderen Sinnes, z. B. des Gehörsinnes, verheilt würden, eine Reizung des Auges eine Tonqualität zur Folge hätte, während jede Farbenerscheinung unterbliebe.” (Brentano, Psychologie, 3:61.) While the passages I quote from volume 3 of Brentano’s Psychologie seem to me to correspond to his overall views on the senses and their objects, it should still be noted that this volume has been edited by Oskar Kraus, who was not always faithful in his editorial work, especially because he was combining in the same text elements coming from several manuscripts (as he himself states, e.g., in Brentano, Psychologie, 3:146).
“[Locke] wollte zwischen Rot und Blau keine größere Verwandtschaft als zwischen Rot und dem Ton c in der Skala finden. Wenn wir jene zusammenrechneten, diese trennten, so sei es nur, weil sie uns durch verschiedene Organe (Auge und Ohr) vermittelt würden. Und das bedeutet nach ihm ‘Farbe,’ ‘Ton’: ‘ausschließlich durch das Auge (Ohr) empfangener Empfindungsinhalt’.” (Brentano, Descriptive Psychology (1887/88) [ms. Ps 76]: n°58207–8.)
John Locke, An Essay Concerning Human Understanding (Oxford: Clarendon Press, 1975), 3.4.16.
Brentano, Descriptive Psychology (1887/88) [ms. Ps 76]: n°58494.
“Denken wir uns eine Sehnervenfaser so mit einer Gehörnervenfaser verheilt, dass der zentrale Teil dem Gehörnerven angehörte, der periphere dem Sehnerv, so würde durch das Licht, welches die Retina reizt, eine Schallempfindung entstehen; dasselbe Endgebilde, welches jetzt der Erweckung einer Farbenerscheinung dient, würde der Erweckung einer Schallempfindung dienen.” (Brentano, Descriptive Psychology (1887/88) [ms. Ps 76]: n°58495–96.)
Brentano, Descriptive Psychology (1887/88) [ms. Ps 76]: n°58496–97. Brentano notes en passant that we have an indirect empirical confirmation of this nerve crossing, namely between sensitive nerves and muscle nerves. For more on this (complex) issue, that I will not treat here, see ibid., n°58297–314.
“Aristoteles hatte geltend gemacht, daß es in jeder der qualitativen Gattungen zwei Extreme gebe, wie z. B. bei den Farben Schwarz und Weiß, bei den Tönen – ein Extrem von Hoch und Tief” (Brentano, Psychologie, 3:62; see also Untersuchungen zur Sinnespsychologie, 161).
See de An. 2.11, 422b27–32, trans. Shields, as well as Shields’s commentary, which I follow on the idea of the subordination.
See Aquinas, Sent. De an. 2.22; see also Aquinas’s solution there, which I will not present. As indicated by Gauthier, Aquinas could have referred, in addition, to Ph. 1.6, 189a13–14, and 189b25–26; see notably 189b25–26: “for in a single genus there is always a single contrariety, all the other contrarieties in it being held to be reducible to one” (
Richard Sorabji, “Aristotle on Demarcating the Five Senses,” Philosophical Review 80:1 (1971): 68n34. Sorabji refers to GC 2.2, 329b34, and 330a24–26. See chapter one above for discussion.
Brentano, Untersuchungen zur Sinnespsychologie, 157. In his Habilitation, Brentano held that Aristotle admits six senses (Die Psychologie des Aristoteles, 85), quoting de An. 2.11, 423b26–29.
F. A. Trendelenburg, In De anima, ad 422b23 (in Aristotle, De anima, ed. F. A. Trendelenburg, 2nd ed. (Berlin: W. Weber, 1877), 330), also referring to Aristotle, GC 2.2.
See again de An. 2.11, 422b27–32, quoted above.
For Brentano’s rejection of another criterion, found in Helmholtz, according to which there is no progressive transition from one sensible quality to that of another genus, see Brentano Untersuchungen zur Sinnespsychologie, 158–61. As stressed by Massin “Brentano on Sensations and Sensory Qualities,” 92–93, Brentano was initially quite sympathetic to this view; see Brentano, Psychologie, 1:213–14.
On colours in contemporary philosophy, see Barry Maund, “Color,” in Stanford Encyclopedia of Philosophy, ed. E. N. Zalta (2018),
See Brentano, Untersuchungen zur Sinnespsychologie, 75–76; id., Deskriptive Psychologie, 118–19; and id, Descriptive Psychology (1887/88) [ms. Ps 76]: n°58218–19, and 58537.
Note that the abovementioned saturation found both in colours and sounds is also described by Brentano as a case of analogy (Descriptive Psychology (1887/88) [ms. Ps 76]: n°58012–13).
Brentano, Von der mannigfachen Bedeutung, 85–98.
See, e.g., Metaph. 9.6, 1048b6–8. On analogy in the Aristotelian tradition, see Jean-François Courtine, Inventio analogiae: métaphysique et ontothéologie (Paris: Vrin, 2005).
Anton Marty, Untersuchungen zur Grundlegung der allgemeinen Grammatik und Sprachphilosophie (Halle: Max Niemeyer, 1908), 503–4.
I thank Pavel Gregoric for having drawn my attention to this text.
Brentano, Untersuchungen zur Sinnespsychologie, 215n17; see also id., Descriptive Psychology (1887/88) [ms. Ps 76]: n°58533.
[…]
At least if one reads the Greek from 448a16–17 following Biehl, Mugnier, and Siwek (l. 17:
Thomas Aquinas, Sentencia libri De sensu et sensato, ed. R.-A. Gauthier (Rome: Commissio Leonina / Paris: Vrin, 1984), 1.16.
“Eo enim modo quo gustus sentit dulce, visus sentit album, et sicut visus nigrum, ita gustus amarum” (Thomas Aquinas, Sent. Sens. 1.16, 91.186–88). Note that Aquinas was using the translation of William of Moerbeke, in which it is not said that sweet differs more from black than from white (the translation is found in the Leonina edition of Aquinas’ commentary).
Gregoric also treats the relation between coordinate sensible qualities in Aristotle as a case of ‘analogy.’ Moreover, he talks of sensible qualities as forming a “qualitative spectrum between a positive and a negative extreme, that is, the state and its privation” (Pavel Gregoric, Aristotle on the Common Sense (Oxford: Oxford University Press, 2007), 134; see also ibid., 135, and 159).
See Brentano, Psychologie, 3:62; id., Untersuchungen zur Sinnespsychologie, 161–62; and Descriptive Psychology (1887/88) [ms. Ps 76]: n°58530–31.
It should be noted that “high” and “low” are used here not for sounds, but as umbrella terms for the two types of ends, positive and negative, of the qualitative spectra.
Brentano, Psychologie, 3:63; id., Untersuchungen zur Sinnespsychologie, 162.
“So zeigt sich, im Gegensatz zu dem, was man vermutete, daß Druckempfindung und Temperaturempfidung von einer Gattung sind. Es ist dies daraus ersichtlich, daß die gleichzeitige Temperaturempfindung einen Einfluß auf die Schätzung der Größe des Druckes übt. Wenn man einen Taler erwärmt und einen anderen abgekühlt auf die Hand legt, so erscheint der zweite bedeutend schwerer. Es hat dies darin seinen Grund, daß die Druckempfindung zu den hellen Empfindungen gehört so wie die Kühleempfindung. Es geschieht hier ähnliches, wie wenn die Beimischung heller Farben oder Töne eine Farbe oder einen Ton selbst heller (höher) schätzen läßt, während die einer dunklen Empfindung im selben Sinn zu einer Unterschätzung der Helligkeit führt. Ähnliches zeigt sich, wenn Zuckerwasser bald kalt, bald warm genossen wird, das kalte erscheint süßer, das warme minder süß. Und wieder gilt dasselbe beim Salzigen und Sauren, wogegen beim Kaffee, der bitter ist, die Kälte den Geschmack eigentümlich verändert, so daß er eher säuerlich als bitter schmeckt. Die Bitterkeit wird durch die Kälte aufgehellt. Verfolgt man dies weiter, so kommt man zum Ergebnis: der Sinn für Farben und ebenso der Sinn für Töne sind als je ein besonderer abzuscheiden. Aber alle die sog. niederen Sinne sind ein einheitlicher Sinn.” (Brentano, Untersuchungen zur Sinnespsychologie, 162.)
On colour mixtures and Brentano’s “chessboard,” see Olivier Massin and Marion Hämmerli, “Is Purple a Red and Blue Chessboard? Brentano on Colour Mixtures,” The Monist 100:1 (2017): 37–63.
Brentano, Psychologie, 3:63.
Sens. 4, 440b29.
“Ohne in so allgemeiner Weise sich auszusprechen, gibt der gemeine Mann doch im Einzelnen dem Zeugnis. Er meint, bei vielen Speisen hätten Geschmack und Geruch eine Verwandtschaft, z. B. beim Essig. Noch frappanter sind Äußerungen, wo der Geschmack von etwas charakterisiert wird durch die Ähnlichkeit mit dem von etwas Anderem, was nie anders als mit der Nase verkostet wurde, z. B. ‘Es schmeckt wie Mäusedreck.’ Oder wie mir neulich eine Dame sagte: Schnecken schmeckten wie Moos.” (Brentano, Descriptive Psychology (1887/88) [ms. Ps 76]: n°58506–7.)
See, e.g., Brentano, Descriptive Psychology (1887/88) [ms. Ps 76]: n°58529–35, where he discusses the pairs of opposites of the sense of feeling, but without labelling them.
Brentano, Descriptive Psychology (1887/88) [ms. Ps 76]: n°58267 and 58536–37.
For more on this, see Massin, “Brentano on Sensations and Sensory Qualities,” 93–95.
Brentano, Descriptive Psychology (1887/88) [ms. Ps 76]: n°58481.
See de An. 2.12, 424a17–28; ibid., 3.1, 424b22–425a13, trans. Shields.
Myles Burnyeat, “De anima II 5,” Phronesis 47:1 (2002): 45. For the claim that secondary qualities in Aristotle are real, causes of sensation, and basic, see Sarah Broadie, “Aristotle’s Perceptual Realism,” Southern Journal of Philosophy 31, Supplementary Volume: Ancient Minds (1993): 137–59; Burnyeat, “De anima II 5,” 45n44 adopts the same view. For the claim that they are real and are causes, but that they supervene on or are reducible to other entities, see Justin Broackes, “Aristotle, Objectivity and Perception,” Oxford Studies in Ancient Philosophy 17 (1999), esp. 102–13. For a defence of the realist interpretation against recent attacks, see Victor Caston, “Aristotle on the Reality of Colours and Other Perceptible Qualities,” Res Philosophica 95:1 (2018): 35–68. On colours in Aristotle (and Alexander of Aphrodisias), see Katerina Ierodiakonou, “Aristotle and Alexander of Aphrodisias on Colour,” in The Parva naturalia in Greek, Arabic and Latin Aristotelianism, ed. B. Bydén and F. Radovic (Cham: Springer, 2018), 77–90.
See Aquinas, Sent. De an. 2.6, and 13, as well as Trendelenburg, In De anima, ad 415a20, 287–88.
See, among others, Myles Burnyeat, “Is an Aristotelian Philosophy of Mind still Credible?” in Essays on Aristotle’s De anima, ed. M. C. Nussbaum and A. Rorty (Oxford: Clarendon Press, 1995), 15–26; and Richard Sorabji, “From Aristotle to Brentano: The Development of the Concept of Intentionality,” Oxford Studies in Ancient Philosophy, Supplementary Volume (1991): 227–59. For a presentation of the debate and an alternative attempt of resolution, see Victor Caston, “The Spirit and the Letter: Aristotle on Perception,” in Metaphysics, Soul, and Ethics: Themes from the Work of Richard Sorabji, ed. R. Salles (Oxford: Oxford University Press, 2004), 245–320.
“[…] die Unterordnung des Begriffspaares, Hören und Tönen, und das des Leidens und Wirkens ⟨ist (my addition)⟩ gänzlich verfehlt” (Brentano, Psychologie, 1:185, trans. Rancurello, Terrell, and McAlister, 101, slightly modified). On these issues, see again Taieb, Relational Intentionality.
Interestingly, however, Sorabji, in his systematic defence and development of Aristotle’s theory of the classification of the senses, holds that phenomenological elements should be taken into account, in order, among other things, to include cases such as hallucinations in the genus of sight: “It looks as if the character of the experience is an important element in the concept of sight. And part of the reason why it is helpful to mention the sense objects in a definition of sight is that reference to the sense objects implies in turn a reference to the kind of experience to which the sense objects give rise.” (Sorabji, “Aristotle on Demarcating,” 67.)
On these difficult issues, see notably de An. 2.9, 422a6–7; Sens. 5, 442b28–443a3; and the discussion in Thomas K. Johansen, Aristotle on the Sense-Organs (Cambridge: Cambridge University Press, 1997), 227–42, whom I follow here.
I thank Robert Roreitner for having drawn my attention to this last point.
See, e.g., de An. 3.1, 424b27–28.
De An. 3.12, 434b18–19.
De An. 2.9, 421a31–b1; cf. ibid., 2.10 and 2.11. On all this, I follow Sorabji, “Aristotle on Demarcating,” 69–75. For a discussion of Aristotle’s (and Alexander of Aphrodisias’) views on the identification of the senses, especially on the importance of criteria other than that of the variety of sensible qualities, see chapter one above.
See Aquinas, Sent. De an. 2.22, quoted above.
Note also that water has its highest density around 4°C and the density decreases the warmer or colder it becomes. Perhaps this fact played a role in Brentano’s experiment. I thank Pavel Gregoric for having drawn my attention to this point.
Brentano, Deskriptive Psychologie, 28–77.
I thank Juhana Toivanen for the example of the sad melody.
Brentano, Untersuchungen zur Sinnespsychologie, 163; id., Deskriptive Psychologie, 116.
Brentano might be referring to Ewald Hering, Über Newton’s Gesetz der Farbenmischung (Prague: F. Tempsky, 1887), 70–71.
Brentano, Descriptive Psychology (1887/88) [ms. Ps 76]: n°58555–56; see also n°58407 for another discussion of the physiological substratum.