1. Introduction

1The nineteenth century saw an Aristotelian revival which was most manifest in philology and exegetic analysis1. The leading proponent of this revival was Franz Brentano, who set out an original interpretation of Aristotle in his book On the Several Senses of Being in Aristotle2 and was himself an Aristotelian in the systematic sense, given that he developed his theory of intentional reference on specifically Aristotelian bases. The writings of particular interest to Brentano were Metaphysics3 and De Anima4, texts which provided him with a linkage to his studies on empirical psychology5.

2Brentano’s studies on Aristotle are of a complexity such that they can be analysed along various dimensions:

1. Environmental (specifically, the relationship between Brentano and the exponents of the Aristotelian revival, in particular Zeller, Prantl, Trendelenburg and Bonitz).

2. Psychological (the connections between psychology and physiology, the problem of the intensity of the sensations and their measurement, the debate on intensive and extensive magnitudes, etc.).

3. Metaphysical (in particular, the theme of being with regard to the categories and the relationship between being-in-potency and being-in-act, between accident and substance, and the problem of the continua)6.

4. Logico-ontological (the theme of being with regard to true or false being, accidental being, etc.).

3These various dimensions are interconnected, so that analysis of Brentano’s writings furnishes a sort of ‘diorama’ on the Aristotelian themes addressed by the nineteenth century’s Aristotelian Renaissance.

4This essay examines a number of aspects relative to psychology and, to some extent, metaphysics which distinguish not only the thought of Brentano but also that of his school–as regards both descriptive psychology and experimental psychology7.

5Specifically, Brentano’s book The Psychology of Aristotle8 marks his shift of interest from metaphysical questions to problems of a gnoseological and psychological nature, although these latter are still presented in the form of commentary on, and interpretation of, Aristotle’s theories. The book acts as a prelude to Psychology from an Empirical Standpoint9, Brentano’s best-known work, and it also marks the point at which Brentano’s interest turned to psychophysical questions10.

6In this paper, after a brief overview of Aristotle’s theory of the soul (in particular of the sensitive soul)11 – which constitutes Brentano’s conceptual framework – I shall outline Brentano’s psychological theories. I shall then examine his specific conceptions, focusing on the difference between psychic phenomena and physical phenomena, and on the part/whole relation which characterizes the former. The Brentano texts to which I shall refer are The Psychology of Aristotle, Psychology from an Empirical Standpoint, and Descriptive Psychology.

7Thematically, Aristotle’s De Anima was addressed during the twentieth century on the basis of three fundamental topics:

The concept of the soul as a non-material bearer.
The concept of the psychophysical subject.
The concepts of psychic phenomenon.

8Here I shall deal with topics 2 and 3. These centre on the concepts of sensation and/or perception, and they are those that link most closely with the problem of psychophysics. I shall therefore not be directly concerned with aspects to do with the connection between knowledge and metaphysics, the doctrine of the nous poietikos connected with the imagination and its relationships with the intellective soul, or more generally with the problem of representation in the broad sense. I shall consequently confine my treatment to what in contemporary terms we may call the primary psychic processes, or in Brentanian terms presentation (Vorstellung) in the strict sense.

9Aristotle states with regard to the soul that:

the soul is that whereby we live and perceive and think in the primary sense; so that the soul would be the notion of form, and not the matter or substrate [...] It is not a body, it is associated with a body, and therefore resides in a body, and in a body of a particular kind.12

10And later:

The soul is the cause and first principle of the living body [...] Lastly, the soul is the primary source of locomotion; but this capacity does not belong to all living creatures. Change of state and growth are also due to the soul; for sensation is held to be change of state, and nothing feels which has not a soul.13

11Again in De Anima, Aristotle defines sensation as an ‘undergoing’ or ‘being moved’ by the sensed object within a process of assimilation which makes perceiver and perceived similar. In Aristotle’s words:

sensation consists, as has been said, in being moved and acted upon; for it is held to be sort of change of state. Now some say that like is affected only by like. But the sense in which this is possible or impossible we have already stated in our general account of acting and being acted upon. The question arises as to why we have no sensation of the senses themselves; that is, why they give no sensation apart from external objects, although they contain fire and earth and the other elements which (either in themselves, or by their attributes) excite sensation. It is clear from this that the faculty of sensation has no actual but only potential existence [...] To begin with, let us assume that being acted upon and moved is the same as exercising the function; for movement is a form of activity, though incomplete, as has been said elsewhere. The sentient subject, as we have said, is potentially such as the object of sense is actually. Thus during the process of being acted upon it is unlike, but at the end of the process it has become like that object, and shares its quality.14

12According to Aristotle, therefore, sensation is dynamically realized in a process of growth/diminution and alteration15 where the soul receives the immaterial form of the external object, realizing the actuality of something initially present within it in potential. Aristotle writes:

We must understand as true generally of every sense (1) that sense is that which is receptive of the form of sensible objects without the matter, just as the wax receives the impression of the signet ring without the iron or the gold, and receives the impression of the gold or bronze, but not as gold or bronze; so in every case sense is affected by that which has colour, or flavour, or sound, but by it, not qua having a particular identity, but qua having a certain quality, and in virtue of its formula; (2) the sense organ in its primary meaning is that in which this potentially lies. The organ and the potentiality are identified, but their essential nature is not the same. The sentient subject must be extended, but sensitivity and sense cannot be extended; they are a kind of ratio and potentiality of the said subject. From this it is also clear why excess in the perceptibility of objects destroys the sense organs; for if the excitement of the sense organ is too strong, the ratio of its adjustment (which, as we saw, constitutes the sense) is destroyed; just as the adjustment and pitch of a lyre is destroyed when the strings are struck hard. It is also clear why plants do not feel, though they have one part of the soul, and are affected to some extent by objects touched, for they show both cold and heat; the reason is that they have no mean, i.e. no first principle such as to receive the form of sensible objects, but are affected by the matter at the same time as the form. One might wonder whether anything that cannot smell is affected at all by smell, or that which cannot see by colour; and in the same way with all other sensible objects. But if the object of smell is smell, if anything affects the sense of smell, it must be smell, so that it is impossible for anything which cannot smell to be affected by a smell; and the same argument applies to the other senses; nor can any of those things which can be acted upon be affected except in so far as is equally clear from the following argument. For neither light and darkness, nor sound, nor smell affects bodies at all: it is the objects in which they reside that produce the effect, just as it is the air with the thunderbolt that splits the timber. But it may be said that tangible objects and flavours do affect bodies; otherwise, by what could inanimate objects be affected and altered? Will then the objects of other senses affect things? Perhaps it is not every body that is affected by smell and sound. The things affected are indefinable and impermanent, such as air; for it smells as though affected somehow. What, then, is smelling apart from being affected in some way? Probably the act of smelling is an act of perception, whereas the air, being only temporarily affected, merely becomes perceptible.16

13It seems from this passage that for Aristotle being affected is already a sort of cognitive state, in the sense of becoming aware of a colour, a sound, etc.

14As to the object of sensation, Aristotle distinguishes three ways in which something can be called sensible.

In discussing the several senses we must speak first of their respective objects. The term «object of sense» is used of three types; two of them we say that we perceive directly, one indirectly. Of the first two, one is an object proper to a given sense, and the other is an object perceptible by all the senses. By proper object I mean that which cannot be perceived by any other sense, and concerning which error is impossible; e.g., sight is concerned with colour, hearing with sound, and taste with flavour. Touch, of course has many varieties of objects. Each sense has its proper sphere, nor is it deceived as to the fact of colour or sound, but only as to the nature and position of the coloured object or the thing which makes the sound. Such objects we call proper to a particular sense, but perception of movement, rest, number, shape and size is shared by several senses. For things of this kind are not proper to any one sense, but are common to all; for instance, some kinds of movement are perceptible both by touch and by sight. I call an object indirectly perceived if, for instance, the white thing seen is the son of Diares; this is a indirect perception, because that which is perceived (the son of Diares) only belongs incidentally to the whiteness. Hence the percipient is not acted upon by the thing perceived as such. But of the per se perceptible those are most strictly perceptible which are proper to a given sense, and it is to these that the special nature of the several senses is adapted.17

15Analytically, then, Aristotle distinguishes among:

16Proper sensibles or proper objects of sensation, accidental qualities perceived by individual senses: i.e. colour, sound, taste, degree of resistance, etc. These are always true in the time of presentness. A misperception in this case can only concern the extension and the place of the perceived18.

17Common sensibles or objects common to more than one sense (koina). These are cross-modality sensed and constituted by the relations among objects: i.e. movement, stillness, unity, number, figure, magnitude. Common sensibles can be true or false19.

18Sensibles per accidens instead concern the perception of substances (for example Diare’s son) through his accident (this white thing), i.e. coincidental sense objects (kata sumbebekos)20.

19Of the three modes mentioned, only the first and the second concern the sensed as such: specifically, the first because it is the proper and prime object of every sense; the second because it is a secondary object of the senses common to several of them21.

20As regards the proper sensibles in particular, Aristotle assumes that external objects are at the origin of perceptual acts, in the sense that the perceptual faculty comprises potential objects which are brought into being by the encounter with the external environment. Of external objects, moreover, the senses perceive qualities specific to each sense.

21As for the common sensibles, this aspect concerns the unitariness and simultaneity of the assimilative process. Based on the perception of movement (both physical and internal as alteration), in that a given movement is perceived by different senses, it accounts for the individuation and conceptualization of objects by connecting the qualities of the diverse senses.

22Aristotle writes:

but, again, it is impossible that there should be a special sense organ to perceive common sensibles, which we perceive incidentally by each sense, such, I mean, as motion, rest, shape, magnitude, number and unity; for we perceive all these things by movement; for instance we perceive magnitude by movement, and shape also; for shape is a form of magnitude. What is at rest is perceived by absence of movement; number by the negation of continuity, and by the special sensibles; for each sense perceives one kind of object. Thus it is clearly impossible for there to be a special sense of any of these common sensibles, e.g, movement; if there were, we should perceive them in the same way as we now perceive what is sweet by sight.22

23Sensibles per accidens pertain to what we may call perceptual experiences in the broad sense, like tables, houses, people, etc., or in other words, individual substances whose accidents or qualities are given by the proper sensibles, and whose relations are given by the common sensibles.

24Aristotle also emphasises the presence of an inner sense directed towards the internal movements of the sensitive part of the soul which yields both the perception of sensations and self-awareness23.

25Aristotle’s theory of knowledge therefore considers diverse aspects of the sensing process. These aspects concern phenomena relating to external stimuli as well as to sensation in the strict sense and perception and their transition as well. Moreover, his analysis highlights the difference between perceiving an object and perceiving the perception of that object, and the complexity of simultaneously perceiving different objects like, for instance, sound and sweetness (different senses) or sweetness and bitterness (contrasting experiences of the same sense).

26The problem of understanding the process of perceptual assimilation in its complexity, moreover, is unresolved. There are three especially problematic aspects:

271. It is not entirely clear whether the perceptual act accompanies a physiological alteration of the sense organ or whether instead no material process is involved–or whether, that is to say, this is a matter of a physics of pure forms24. What is certain is that the perceptual act in Aristotle does not coincide reductionalistically with the sense organ from time to time affected. Aristotle simply says that the sensitive faculty is in potency that which the sensible already is in entelechy, in the sense that it undergoes an alteration by way of its diversity, and that the process undergone renders it similar to it.

28The problem can therefore be stated as follows. Does the assimiliation of the sentient to the sensible mean, for example, that the sense organ variously becomes sonorous, coloured, etc. according to the proper sensible concerned25? Or does the sensation, via the perceptual act, recognize only the immaterial forms of the sensible quality, as it seems possible to deduce from some of the above-cited statements by Aristotle, and from the fact that Aristotle talks of assimilation in the strict sense only in relation to the distinction between potency and act?

292. Secondly, still undecided is the direction of the process: that is, does the assimilative process start from the exterior, in the sense of the affection of the soul by stimuli, or does it follow the reverse process, namely that of a sensitive activity which starts from internal formal articulations and tends towards external objects26?

303. Thirdly, it is not clear what role is performed by the transparent means that enables vision – what in Theophrastus’ terminology is called the transaudible and the transodorous27.

31Aristotle writes:

The object of sight is the visible. This is either colour, or something which can be described in words, but has in fact no name; what we mean by this will become quite clear as we proceed. The visible, then is colour, i.e. that which overlies what is in itself visible; by «in itself» we mean not that the object is by definition visible but that it has in itself the cause of its visibility. Every colour can produce movement in that which is actually transparent, and it is its very nature to do so. This is why it is not visible without light, but it is only in light that the colour of each individual thing is seen.
Consequently we must explain in the first place what light is. Transparency evidently exists. By transparent I mean that which is visible, only not absolutely and in itself, but owing to the colour of something else. This character is shared by air, water and many solid objects; it is not qua water or air that water or air is transparent, but because the same nature belongs to these two as to the everlasting upper firmament. Now light is the activity of this transparent substance qua transparent; and, wherever it is present, darkness also is potentially present. Light is then in a sense the colour of the transparent, owing to fire or any such agency as the upper firmament; for one and the same quality belongs to this also.28

32Between sensation and the sensed, potency and act, there exists in fact an intermediate phase which is a correlate of the sensation itself given by the medium involved and which enables transmission of the form. In other words, we are able to perceive the form and not directly the activity of the external stimulus, so that the object of the sensation is the means and not the colour, sound, and so on. If this aspect of the assimilative process is emphasised, the interpretation of Aristotle’s De Anima as strietly physiologically oriented obviously no longer holds.

33It is evident from these considerations that Aristotle’s theory covers a number of themes which link directly with nineteenth-century psychophysics, particularly as regards the distinction between stimulus and perception of forms, and also as regards the differences among the diverse formats of representation (sensation, perception, representation, judgement, etc.) and its various phases.

34In particular, readings and interpretations of Aristotle’s De Anima highlight one of the issues still discussed in contemporary debate, namely the problem of bottom-up or top-down reductionism in analysis of the perceptual process.

35In general, Aristotle’s texts seemingly offer three options with regard to the nature of the assimilative process:

• A physiologically oriented interpretation (i.e. the sight organ becomes coloured under the effect of the colour).

• A symbolic or representational interpretation of neo-Platonic stamp (i.e. the internal activity is directed towards external objects)29.

• An interpretation which I call embryonically phenomenological of Theophrastian origin (i.e., there is a medium between stimulus and perception which enables its assimilation in terms of continuity although not being directly ‘affected’ by it)30.

36Whatever the case may be, the fundamental problem with the perceptual process remains that of the nature of the stimulus, for both Aristotelian science and contemporary science. To quote one of the leading exponents of contemporary psychophysics:

In a sense, there is only one problem of psychophysics, namely the definition of the stimulus. In the same sense there is only one problem in all of psychology–and that is the same problem. The definition of a stimulus is then a bigger problem than it may appear. At first sight the reason for equating psychophysics to the problem of defining stimuli can be stated thus: the complete definition of a stimulus to a given response involves the specification of all the transformations of the environment, both internal and external, that leave the response invariant.31

37Many centuries later, therefore, the problem posed by Aristotle, and the terms in which he did so, have still not been resolved.

38In the nineteenth century, early psychophysicists added to the themes that – in Aristotelian terms – define the scope of psychology as the science of the soul the experimental problem of how to measure psychic phenomena.

2. Psychophysics between Aristotle, Fechner and Brentano

39Contemporaneously with the Aristotelian revival, which mainly concerned the humanities, Europe (and Germany in particular) saw the birth of experimental psychology. As psychology emancipated itself from philosophy as an autonomous discipline, psychophysics constituted one of its most striking advances. As already mentioned, moreover, psychophysics and Aristotelian studies displayed close thematic correlations.

40Starting from Aristotle’s formulation of the problem of the internal modification of external stimuli, there are substantially four psychophysical options:

• The analysis of the relationship between the external stimulus and the psychic phenomenon.

• The analysis of the relationship between the external stimulus and the physiological reaction (internal stimulus).

• The analysis of the relationship between the physiological reaction and the psychic phenomenon (inner perception).

• The analysis of the relations between the previous three cases (external psychophysics and internal psychophysics).

41Broadly speaking, these four options correspond to the conceptualizations of Weber, Lotze, Brentano and Fechner. In other words, each of these authors analysed a particular aspect of the problem, or better a particular component of the psychophysical relationship between body and mind.

42The connections with the psycho-physiological theory of the mind developed by nineteenth-century psychophysics largely reflect Aristotle’s theory, complicated by the debate on the extensive and intensive qualities envisaged therein, on whether or not the soul is a magnitude, and if so of what kind, and on its relationship with the body32.

43In particular, psychophysical analysis:

• Treats the process by which, according to Aristotle, external stimuli are modified by the inner sense as a subjective sense which registers the muscular changes due to sensations in kinaesthetics.

• Calls the proper sensibles, those involved in the passage of external stimuli to the nervous system via excitation of stimuli internal to the sentient being, pure sensations (light, dark, colour, etc.).

• Ascribes to the common sensibles, which more properly concern inner perception and in particular the perception of forms at rest, in motion, etc., a representative element due to the insertion of sensations in a spatial, temporal and numerical framework.

44The birth of psychophysics is principally associated with the names of H. Weber and T. Fechner, and it is summed up in the Weber-Fechner law, despite the different metaphysical options on which inquiries of those two authors are based. Weber, in fact, opted in favour of extensive magnitudes, while Fechner envisaged only intensive ones. The debate, in which also Herbart and Lotze took part, prefigures Brentano’s psychological theory of the soul.

45As regards the general features of extensive and intensive magnitudes, here I shall refer to Stevens’ classification of magnitudes into prothetic and metathetic33, restricting their meaning to the ambit of psychophysics, given that the authors of the period used the term in senses which differed according to (i) the context (physical, psychic, metaphysical) and (ii) the relevant vocabulary (natural, scientific or metaphysical language).

46Stevens’ distinction concerns various aspects of the perceptual continua. He points out the difference in behaviour apparent in, for example, the auditory continuum between loudness and pitch. The former can be described in terms of degrees of magnitude, or of quantity (prothetic continuum), while the latter varies from high to low, has a position, and can be described in terms of quality (metathetic continuum)34.

47In short, we can characterize extensive magnitudes as follows:

• They are extended (they always exist between two points).

• They are mutually external.

• They can be summed (aggregates) and are therefore additive.

• The whole contains smaller parts (parts are prior to the whole).

• They have a prothetic order (quantitative, based on ‘more than’).

48In other words, extensive magnitudes concern ‘how much’.

49In complementary manner, intensive magnitudes can be characterized thus:

• They are not necessarily extended (they may be punctiform in nature).

• They are functionally co-dependent.

• They cannot be summed and are therefore substitutive.

• They do not contain smaller parts of the same nature (i.e. non-homogeneous) (the whole is prior).

• They have a metathetic or positional order (qualitative, based on ‘different from’).

50In other words, intensive magnitudes concern ‘where and how’.

51Examples of extensive qualities are volumes, which can contain other volumes as their parts (more than). Examples of intensive qualities are colour, because the colour of the whole is not the sum of the colours of its parts (it can at most be the pattern of its parts), or a tactile stimulus which we notice as it moves from one part of the body to another (different from).

52From a general point of view, psychophysics seeks to establish a quantitative relationship between the sensory input of the stimulus and the perceptual output, or the magnitude of the reaction. In other words, it seeks to determine the dependence between external stimulus and internal information processing.

53Weber’s psychophysical law for the measurement of psychic magnitudes states that if differences are to be perceived between stimuli applied to a sense organ at different intensities, the differences must reach a certain value (threshold) which is proportional to the intensity of the initial stimulus. Under Weber’s law, therefore:

The difference in the intensity of the sensations is expressed as a function of the intensity of the stimulus.
A correlation is established between physical quantities and psychic quantities.

54A prominent role is played in psychophysical inquiry by differential discrimination, or in other words, by the discriminant of the difference between sensations perceived as greater or lesser. It is characterized by the following two features:

Increment in a series (the musical scale or the colour scale, for instance, and internally to them by orders differing according to pitch, position, purity, bright ness, etc.).
The assumption of uniform direction.

55In other words, in differential discrimination we perceive a serial increment of differences in which the difference (distance as Stumpf called it, or interval)35 between any two terms in a series is greater than that between any two of their intermediate terms. Moreover, each of these differences is perceived as a specific sensible quality, so that the second object compared is never sensed in pure manner with respect to the first, but as ‘different from’ it36.

56Consider what happens when 1 gramme is added to 10 grammes or 1 gramme to 10 kilos. The perception of the difference in increment will not be the same. Conversely, if we add 1 gramme to 10 grammes and 1 kilo to 10 kilos, the difference will be perceived as conceptually equivalent. Consequently, Weber claims that, in noticing the difference between the qualities that we are comparing, we do not perceive the absolute difference between them, but rather the relation of difference with the absolute magnitude of the things compared37.

57On the basis of Weber’s analyses, Fechner set out his programme for a psychophysics conceived, as he put it, as an exact science of the soul38. His analysis concentrated on the characteristics of sensation, in an endeavour to arrive at a numerical quantification of sensory experience whereby every unit of sensation, of whatever kind, comes to coincide with that increment which, when the stimulus is increased, we are barely able to perceive. This number is not achievable directly, but only indirectly via the physical stimulus.

58Consequently, Fechner distinguishes between:

External psychophysics (which concerns the mediate relation between external stimuli and psychic phenomena).
Internal psychophysics (which concerns the immediate relation with the nervous system, and therefore physiology amid psychic phenomena).39

59Fechner was mainly concerned with analysis of external psychophysics, where the measurement of psychic phenomena came about indirectly by measuring the stimuli on the basis of their functional relation. This relation, Fechner believed, could be identified and expressed exactly, although the magnitude of a sensation could not be determined or gauged directly.

60What is known in the literature as the Weber-Fechner Law is in effect the law formulated by Fechner, which states that the intensity of sensations is expressed as a function of the intensity of the stimuli, establishing a (presumed) correlation between physical magnitudes and psychic ones consisting in a ‘psychophysical transformation’ of the increase in intensity of external stimuli into the increased intensity of the sensation.

61For these various reasons, the sensory characteristics studied by classical psychophysics are basically thresholds, which are of two types:

621. Absolute threshold

63This is the minimum intensity of the stimulus necessary for the specific sensory stimulus to be sensed (for example, the perception of a light with an extremely low intensity electromagnetic wave; or the chromatic colour of a light with a higher intensity electromagnetic wave).

64Measurement is by its nature statistical, and consequently the absolute threshold is defined as the intensity of stimulus necessary to arouse the corresponding sensation in fifty percent of presentations40.

652. Differential threshold

66Also known as ‘just noticeable difference’ (jnd), this is the minimum increment or intensity that needs to be added to a stimulus for it to be noticed that the new stimulus is different. Weber found that the fraction (jnd)/(intensity of the stimulus) is largely constant for all types of sensation, although its value changes according to the type of sensitivity considered41. Deviation from this law, in fact, arises when the stimulus is very weak or very intense42.

67The assumptions underpinning classical psychophysics were therefore the following:

• There is a causal relationship between stimulus and perception.

• The increase in the stimulus necessary to produce an increase in the sensation stands in a constant ratio to the total stimulus.

• Our sensations are given compositionally by a sum of the units of sensation (jnd).

• The correlation between the constant increment and unity of sensations is determined by a law of psychophysical connection between mind and matter43.

68The true problem with the psychophysical law, however, resides in the relationship between two types of continua – the physical continuum of the stimuli and the sensory continuum – which need not necessarily be homogeneous nor coincide in a single scale. The former, in fact, is quantitative in character and therefore summative (increased intensity of the stimulus = new neural excitation which adds itself to the ongoing excitation). The latter is qualitative, substitutive and therefore positional, and involves the perception of difference and therefore a judgement. Moreover, it is not true that the various jnd give rise to an invariably constant increase in the sensation; rather, they increase in relation to the intensity of the stimulus.

69It is evident in the light of these considerations that, from a systematic point of view, the claims and the problems raised by Fechner’s psychophysics involve aspects which were also characteristic of Aristotle’s theory of the soul, and notably the relationship among:

• Psychophysical activity and sensation.

• Psychophysical activity and the conscious psychic phenomenon.

• The quantitative and qualitative difference among phenomena.

• The perception of stimuli and the perception of difference.

• The relationship and difference between increase/diminution and alteration (i.e., two different aspects of movement in Aristotle).

70These various aspects, mediated by Lotze’s theories44, converged in Brentano’s Psychology from an Empirical Standpoint, one of whose points of departure was a critique not so much of Weber’s law as of Fechner’s psychophysics, the psychological outcome of which, as is well known, James dismissed as nil45.

3. Brentano on the soul

71It was Brentano’s Aristotelian studies that prompted him to develop and differentiate those aspects that Fechner had defined as pertaining to inner psychophysics (the immediate relation between the nervous system and psychic phenomena) and which dominated scientific psychology in its nineteenth-century beginnings (so-called ‘physiological psychology’). Brentano’s analysis, in fact, focused on phenomenal appearances as further modifications of internal stimuli due to the structure of the act of intentional reference46. The true contribution of Brentano and his school, indeed, consisted in analysis of the organization of the elementary sensations into temporal and spatial patterns imposed by the structure of consciousness47.

72The principal component of Brentano’s legacy from Aristotle was his recognition of the existence of an active corporeal quality which is the medium for every other sensation and a modification of the sensory content48. Like Aristotle, he took the assimilative process to be the internalization of the surrounding environment and ascribed inner perception with its own laws of organization, which involve the alteration of distal stimuli. He thus established a similarity between the sensed environment and the inner perception of forms, while the soul acts as the bearer of psychic phenomena, although not in the sense of an I.

73For Brentano, the inner sense directly addresses the inner movements of the assimilative process (as also Lotze and Weber, besides Aristotle, had emphasised, however mainly from a psycho-physiological point of view). In particular, he ascribes to inner sense the perception of differences between the objects of different senses (for example between something white and something sweet) and the perception of differences within objects (for example between the sharp, angular, red, hot, etc. qualities of something perceived). Thus the consciousness of psychic phenomena coincides with a state of inner perception (innere Wahrnehmung).

74In Psychology from an Empirical Standpoint, Brentano sets out his doctrine of intentional reference and the distinction between psychic and physical phenomena that provoked his criticisms of Fechner’s theories.

75He defines psychic phenomena as acts whose objects have internal or intentional existence and are constituted in the first place by the Aristotelian proper sensibles – coloured, tactile, auditory, etc., appearances – as correlates internal to the act of presentation.

76Psychic phenomena are real and are endowed with evidence. They constitute the inner perception whereby the identity of perceiver and perceived is realized. Brentano also furnishes an original classification of psychic phenomena as acts of:

• Presentation (i.e. being directed at, or having an object of some kind).

• Judgement (i.e. accepting or rejecting the object of the presentation).

• Emotion (i.e. liking or disliking the object of the presentation).

77In Brentano’s words:

Every presentation which we acquire either through sensation or phantasy is an example of psychic phenomenon. By presentation I do not mean what is presented, but rather the act of presentation. Thus, hearing a sound, seeing a coloured object, feeling warmth or cold, as well as similar states of phantasy are examples of what I mean by this term. I also mean by it a general concept, provided such a thing actually does occur. Furthermore, every judgment, every recollection, every expectation, every inference, every conviction or opinion, every doubt, is a psychic phenomenon. Also to be included under this term is every emotion: joy, sorrow, fear, hope, courage, despair, anger, love, hate, desire, act of will, intention, astonishment, admiration, contempt, etc.49

78Physical phenomena, by contrast, are objects of the act. They mainly involve sensible qualities and consist in whatever is seen, felt, heard, etc., no matter whether they are objects of sensation, perception or phantasy. They have dependent phenomenal existence and consequently, and properly speaking, are non-real.

79Brentano puts it thus:

Examples of physical phenomena, on the other hand, are a colour, a figure, a landscape which I see, a chord which I hear, warmth, cold, odour which I sense; as well as similar images which appear in phantasy.50

80It is well known that the status of the physical phenomena that constitute the objects of intentional presentation is one of the most controversial aspects of Brentano’s theory, and especially so since the physicalist conception of the world51. Firstly, according to Brentano, we never come into direct contact with external stimuli, so that physical phenomena are nothing but objects internal to the act of presentation. In other words, presentation of phenomena of whatever type is entirely internal.

81Moreover, with regard to the objects of sensation, from his analyses in the Psychology of Aristotle onwards Brentano emphasised that coldness, for example, is a sensed physical quality which resides in strictly scholastic terms in the person who objectively feels cold52. In other words, we do not feel cold because we are cold (alteration of the subject) but because the cold is within us as a form (object of the act) assumed without matter. What for psychophysics are the sensations, in Brentano’s empirical psychology are objective phenomena of light, colour, weight, sound, etc., i.e., objects of presentation and of judgement53. Consequently, it seems possible to say that at an initial level, that of mere presentation, and therefore of the actual correlate of the act, physical phenomena are to be identified with the proper sensibles, or the sensed qualities.

82For Brentano, moreover, psychic phenomena have at least two different types of objects: primary ones (objects in the proper sense) and secondary ones (the act itself as object, in which inner perception real and proper consists).

83In this regard Brentano talks of a twofold orientation (Dienergie) of every psychic act towards its object and towards itself. However, its orientation towards the primary object does not take ontological priority over orientation to the secondary one. Despite the twofold reference, Brentano stresses, a single psychic phenomenon is involved whose structure manifests the essentially relational character of consciousness. In intentional reference, therefore, we distinguish, for example, ‘seeing-red’ from ‘consciousness of seeing something’.

84Between ‘seeing-red’, the ‘consciousness of seeing something’ and ‘seeing a coloured object’, however, what is sensed undergoes a series of relational modifications which à la Aristotle seemingly give rise to the perception of sensibles per accidens. As Brentano writes in The Psychology of Aristotle:

Finally, Aristotle calls sensible per accidens everything that belongs to a perceived object without determining the sensation in any way. He explains this through an example. Someone sees something light, and it is the son of Diares. Now one could say that he sees the son of Diares, but he does not see him as such; he sees the white object, and it is true of this white which he sees that it is the son of Diares. In this manner, what belongs to the proper objects of one sense is also perceptible by the other senses; one tastes the coloured thing and sees the sounding thing, etc.54

85In what way, therefore, does Aristotle’s classification operate in Brentano’s theory? In my view, it undergoes changes neither as regards the proper sensibles, which in Brentano are still atomic qualities produced by the various sensory fields, nor as regards the sensibles per accidens, which constitute the real ‘perceptual objects’ of our experience.

86But Brentano does elaborate the notion of common sensibles. In both Brentano and Aristotle, in fact, the sensed qualities are modified, in that they are structured by internal relations as they become incorporated into space, time, figure, movement, etc. However, for Brentano this modification is a form of perceptual organization of the initial qualities which gives rise to some kind of ‘closure’ of the sensed and relationally modified qualities in a certain type of ‘object’55. This closure is due to a spatio-temporal schematic structure, the moment-now (Jetzt) or time of presentness. Very interestingly, this structure is susceptible to analysis from both a systematic point of view (as in the case of Brentano and Husserl after him) and an experimental one (as in the case of some of Brentano’s pupils, notably Stumpf and Meinong)56. In fact, as psychophysical research also found, of crucial importance in comparison among judgements on sensations is perception of the temporal interval. Incorporation of the sensible qualities into the time of presentness – i.e. their insertion in a phenomenal spatio-temporal structure – in fact produces a complex modification of the stimuli caused by two factors:

• Increase and diminution (psychophysical).

• Qualitative alteration due to subjective elements (psychic) like the role played by the temporal intervals in construction of the final percept57.

87It is true, however, that the concept of act in Brentano, like that of actual presentation, has always been somewhat obscure. Defined as psychic energy or activity, by Brentano it has never been given specific scientific exemplification. Its Aristotelian ascendancy remains in the sense of:

The form of a natural body, which potentially has life. And substance in this sense is actuality.58

88For both Aristotle and Brentano, for example:

We say then, assuming a fresh starting-point for our enquiry, that that which has soul is distinguished from that which has not by living. But the word living is used in many senses, and we say that a thing lives if any one of the following is present in it–mind, sensation, movement or rest in space, besides the movement implied in nutrition and decay or growth. Consequently all plants are considered to live, for they evidently have in themselves a capacity and first principle by means of which they exhibit both growth and decay in opposite directions; for they do not grow up and not down, but equally in both directions, and in every direction, and they are nourished and continue to live, as long as they are able to absorb food. This capacity to absorb food may exist apart from this in mortal beings. This is evident in the case of plants; for they have no other capacity of the soul.
This, then, is the principle through which all living things have life, but the first characteristic of an animal is sensation; for even those which do not move or change their place, but have sensation, we call living creatures, and do not merely say that they live.59

89All that we learn from Brentano is that the act (the seeing, the hearing, etc.) has directedness (towards the primary and secondary object) and modes (direct and indirect), among which of great importance are the temporal modes60, which do not have intensity or increment and are therefore not susceptible to measurement. Following Weber and Lotze, in fact, and against Fechner, Brentano declares that the acts of presentation are not intensive magnitudes; they exhibit only degrees of greater or lesser clarity which derive from their nature of extensive magnitudes.

90As a consequence, the act takes the form of a spatio-temporal structure saturated to a greater or lesser extent by elements (sensible qualities), more or less empty, whose clarity depends on the threshold of individual perceptibility of the individual qualities and relates to:

• How many and which elementary units of sensation are actually present.

• The mode of their presentation61.

91Indeed, intensity or increment pertains solely to objects, or better to the contents of the act. Only these are susceptible to measurement, and Brentano takes them to be physical phenomena.

92In his words:

Finally, it could be said that a clear understanding of what is actually measured by Fechner’s method would show us that the object of measurement is not so much a psychic as a physical phenomenon. What are physical phenomena if not the colours, sounds, heat and cold, etc.? – So, when we measure the intensities of colours, sounds, etc., as Fechner did, we are measuring the intensities of physical phenomena. Colour is not seeing, sound is not hearing, warmth is not feeling warmth. The reply may be made that even if seeing is not colour, nevertheless its intensity corresponds to the intensity of the colour seen by the subject. The strength of the psychic phenomenon, therefore, would be determined along with the strength of the physical phenomenon. I do not want to deny that this is the case, although, as we shall see later, there are psychologists who distinguish between the intensity of object which is presented and the intensity of the presentation. For my part I admit that if, on the basis of Fechner’s method, a measurement could be found for the physical phenomenon, it could also be found for the psychic phenomenon in which the physical phenomenon is presented. Yet, it seems to me necessary to add the new restriction that only one aspect of the psychic phenomenon should be measured according to its intensity, namely its reference to its primary object, for we shall see that the psychic phenomenon has still other aspects and it is not exhausted by this one reference.62

93Fechner’s prejudice, then, according to Brentano, stemmed from the fact that he confused the perception of the intensity of the sensation (physical phenomenon) with the intensity of the entire act (psychic phenomenon) itself.

94Secondly, although Brentano gives Weber and Fechner due credit for their important discovery of the relationship between the increase in the stimulus and the increase in the sensations, he makes the following criticism of them:

It has been found that the increase of the physical stimulus which produces a just barely noticeable increase63 in the strength of the sensation always bears a constant relation to the magnitude of the stimulus to which it is added. And since it was assumed to be self-evident that each barely noticeable increase of sensation is to be regarded as equal, the law was formulated that the intensity of sensation increases by equal amount when the relative increase of the physical stimulus is the same. In reality, it is by no means self-evident that each barely noticeable increase in the sensation is equal, but only that it is equally noticeable. In addition, the quantitative relationship between equally noticeable increases in sensation remains to be examined.64

95Brentano therefore does not accept a further key assumption by Fechner, namely that all equally perceptible increases are of equal magnitude. He maintains instead that they differ in qualitative, and not merely quantitative, manner, the consequence being that their respective part/whole relationship must be revised, as well as the role played by noting in the presentation65.

96Moreover, Brentano points out, the psychophysical law entirely lacks a measure of intensity for all the physical processes that occur in the organism, and also for the psychic phenomena of desire, will or belief; not to mention the fact that sensations depend not only on the external stimulus but also on subjective conditions like attention or the subjective set (Einstellung), which give rise to a subjective structural modification of the content given66.

97In short, according to Brentano, psychophysics does not directly measure psychic phenomena (acts) but furnishes various measurements of the same physical phenomenon (i.e. of primary objects of the acts)67.

98In this sense, as Stevens notes with regard to Ekman’s development of psychophysical analysis during the 1950s, which drew on Brentano’s ideas,

The principle [Brentano’s] states that, when variability is measured in subjective units, it is linearly related to psychological magnitude measured by the same units. That relation is the analogue of Weber’s law, which concerns the linear growth of variability among human judgments as a function of the stimulus measure. Both Fechner (in deriving his law) and Thurstone [...] proposed a different assumption, namely, that variability in psychological units is constant along the psychological continuum. The Fechner-Thurstone assumption has been found to be adequate for metathetic continua, but not for protothetic continua. As Ekman and his collaborators [...] have repeatedly demonstrated, on prothetic continua the variability in subjective units tends to grow as a linear function of the subjective magnitude.68

99In contrast to Fechner’s law, under Brentano’s reformulation of the body/soul relationship Weber’s law still stands if it is simply considered to be an empirical generalisation valid at the physiological level: i.e., which states that we more easily note what we add to a small stimulus than what we add to a large one, unless the stimulus is of the same magnitude.

100In sum, for Brentano psychophysics is not a science of the soul, as Fechner claimed. Instead, it is merely the analysis of a condition necessary, but not sufficient, to explain the nature of psychic facts. Providing such explanation is instead the task of an empirical psychology, understood as the analysis of the phenomenal appearances given in actual perception and mediated by the underlying physiological processes; the phenomenal appearances emerge from the latter in accordance with the laws of organization imposed by the structure of the intentional reference. In other words, psychophysics analysed the signal in isolation from its context, while Brentano, in accordance with Aristotle, considered both the external signal and the internal affection69.

101For Brentano, therefore, the science of the soul has the specific task of analysing:

• What the soul is (as the bearer of psychic phenomena or consciousness).

• What its (material and spiritual) characteristics are.

• Of what elements it is composed (despite being unitary and simple).

102Brentano dealt with these questions mainly in Descriptive Psychology, which, unlike Psychology from an Empirical Standpoint, exhibits a Cartesian influence and thereby distances itself from psychophysical analysis in the strict sense70, returning in certain respects to Aristotle’s De Anima and to an ontological-descriptive analysis of consciousness71.

4. The parts of the soul

103One of the classic components of psychophysics, the theory of magnitudes, highlighted inter alia the problem of the nature of the relationship between consciousness as a whole and its parts, and also the problem of their separability, real or conceptual.

104Brentano’s account of the unitariness or otherwise of the soul, as a single sentient subject but at the same time endowed with parts, is once again of Aristotelian derivation, and it was already adumbrated in The Psychology of Aristotle72.

105According to Brentano – whose descriptive psychology, as said, conducts an ontological analysis of consciousness – the parts of which the soul is made up are of essentially two kinds:

1. Detachable.

2. Non-detachable.

106Separable parts are acts. They are characterized by intentional reference, which we have seen may be of two types, primary and secondary. Acts are not spatial and they do not have qualitative variation; accordingly, they should not be confused with their correlates. Moreover, they divide into two classes: fundamental acts and superimposed acts.

107The primary objects of fundamental acts are sensory phenomena (which for Brentano as for Aristotle include perceptual presentations, illusions, hallucinations, reflections, after-images, etc.). The fundamental acts also comprise acts of temporal proteraesthesis involving perceptions of motion and stillness, and auditory perceptions like hearing a syllable, a melody, etc.73

108A fundamental act – seeing for example – always has a bipolar act/correlate structure (i.e. the act of seeing versus the cat seen, the light seen, etc.). It is a whole endowed with parts, where the parts are non-independent. Fundamental acts, moreover, have an inner structure. In seeing, for example, the noting of something constitutes the transition from an implicit perception to an explicit one in which the object seen acquires a frame of reference: consider, for example, the difference between seeing a lark in the sky and noting its presence on a balcony, which functions as a frame of reference. Noting is always internal to an act of presentation, and it should not be confused with other states like:

• Being struck (emotional state).

• Taking notice (to fix an impression, gradually).

• Paying attention (disposition to note).

• Memory (where an outright substitution (Stellevertretung) of the object takes place).

109Noting may be absent from an act of presentation and be impeded by various factors, often of a psychophysical nature, like the constant growth or diminution of the magnitudes, spatial or acoustic thresholds, the direct correspondence between parts of the seeing and parts of the seen, distraction, or more simply the perceiver’s incompetence. It may also be impeded by language or prejudice (for example, the perceiver refuses to accept that black is a colour, or that orange is a mixed colour)74, or the temporal quality (too short, too long or contemporaneous).

110Superimposed acts are based on fundamental acts like, for example, the presentation of a general object (a colour, a shape, a particular brightness, etc.), the desire to make a journey (which is always based on a concrete presentation), or non-intuitive presentations (e.g. the presentation of a grey black).

111The detachability of acts can be unilateral or bilateral. Examples of reciprocal detachability are:

• Seeing and hearing.

• Parts of seeing and parts of hearing.

• Seeing and remembering having seen.

112Examples of one-sided detachability are:

• Seeing and noticing.

• Seeing a colour and presenting its concept.

• Concept and judgement.

• Premises and conclusions.

113The other components of consciousness consist primarily of objects of primary reference made up of mutually pervading parts. These may be both:

• Objects of sensation.

• Objects given in the temporal modification of the proteraesthesis.

114In the former case, the parts are present and are both spatially and qualitatively characterized (examples are colours or sounds) and can be conceptually distinguished but not phenomenally separated. In the latter case, the parts are temporally modified (as in ‘seen’ colour, ‘heard’ sound).

115In their turn, the qualities of the parts of the objects of sensation have diversified components: for example, we can have colouredness vs. colourlessness, lightness vs. darkness, saturation vs. unsaturatedness; in other words, we can have something blue-coloured vs. something red-coloured; something red, or blue coloured vs. something grey, black or white; or something sound vs. something soundless.

116Thus, in the case of mutually pervading parts (like space and colour), we can distinguish further (distinctional) parts in the primary objects of sensation, like lightness. Take, for example, the case of two patches of colour given in the actual presentation:

117They are distinguished by:

The place that they occupy.
Colour.
Their respective lightness.

118The place occupied by the objects of the presentation is decisive for their individuation, because if we move the yellow patch to another position, according to Brentano, from the phenomenal point of view it is no longer the same patch but another one with a different determination of colour.

119Colour and space are in fact mutually pervading parts relative to individuals which are inseparable75.

120Now take: two blue patches, a yellow one and a grey one.

121In this case, 1 ≠ 2 as regards place, 1,2 ≠ 3 (as regards colour), 3 is similar to 4 as regards lightness, 1,2 ≠ 3,4 as regards lightness. Colour, place and lightness are thus distinctional parts of the psychic phenomenon.

122Moreover, as Brentano specifies:

Concerning the blue spot, we will hence have to differentiate two things: the particular spatial determination [Örtlichkeit] and the particular quality, i.e. the particular colour. In the blue spot one must therefore distinguish a particularity of colour and a particularity of place [Besonderheit des Orts]. These particularities are thus actually contained in it, [they] are distinctional parts of them.

123Let us go on! Comparing the grey spot, on the one hand, with the yellow one and, on the other, with a blue one, we will in both cases find the double difference which we noticed between the blue and the yellow spot, [namely] the spatial [difference] and the qualitative one. If we have one of the lighter shades of gray before us, it may happen that we find a difference between this grey and the blue which we are unable to discover between this grey and the yellow, and which we call a difference of lightness. As concerns lightness, we equate the given shade of grey with this yellow, whereas we say that it differs in lightness from the given blue.

124So we would have a third thing [evo] which could be distinguished in each of the three spots, and which would have to be referred to as a distinctional part of it:

• spatial particularity,

• particularity of lightness,

• particularity of quality76.

125Thus the science of the soul, by differing itself from Fechnerian pyschophysics, returns to its Aristotelian roots developing their implicit content: namely that of an analysis of the forms assimilated by the soul without the matter, and descriptively analysed.

126Other kinds of distinctional parts are of logical type, including a distinction by genus and specific difference, like place and redness, and the parts of the dyenergy of the act, i.e. its twofold structure (directed toward the primary object and directed toward itself as secondary object. The latter, being effectively non-detachable, can be only distinctionally, i.e., conceptually, analysed).

127The case of the parts of the objects given in proteraesthesis is more complex, because these are modified distinctional parts. For example, in the case of ‘seeing red’, colour is a distinctional part; while in the case of ‘red seen’, colour is a modifying distinctional part of the object (the same holds for ‘sound heard’, etc.).

5. Soul and metaphysics

128As we have seen, Brentano’s analysis of the soul started from his reflections on Aristotle, after which he explored the psychophysical relation from a scientific-experimental point of view, concluding that psychophysics is not a science of the soul and returning to ontological inquiry, albeit mediated by the results of his empirical psychology. As for Aristotle, so for Brentano analysis of the soul, its elements and its laws of internal dependence, led to the boundaries of metaphysics.

129At the basis of Brentano’s distinction among the parts of the soul and their separability and otherwise lay the concept of perceptual space–and even of a proto-modularity spaces–relative to the problem of the continua (primary spatial and temporal), which interested him until the last years of his life77. According to the analyses of his empirical psychology, regarding both psychophysics and the descriptive theory of the soul, in fact, perceiving is a cross-modal spatial process which comes about within a peripersonal, propriocentric space and in which vision is the dominant modality.

130The metaphysical outcomes of Brentano’s analysis of the soul conducted in Psychology of Aristotle, Psychology from an Empirical Standpoint and Descriptive Psychology – the works considered in this paper – led him to the conclusion that the sensible quality (accident) (i.e. the Aristotelian proper sensible), be it auditory, coloured, tactile or whatever, contains place as its ultimate subject (substance), and that accidents attach to the single substance transmitted from one part to another. In this theory, still clearly Aristotelian, the soul in its potential aspects is viewed as a locus of immaterial forms which are altered by their perception.

131Brentano’s analyses subsequent to his reist turn of the early 1900s78 focused on the relationship between quality and spatial place, quality and temporal modification. They induced him to take up a radical position which reversed the Aristotelian relationship between substance and accident, so that the quality of the act of presentation (seeing red, for example) becomes the sole existent reality while simultaneously instantiating the relative spatial continuum79.

132For the late Brentano, that which exists in the proper sense is only the psychic act of the concrete presentation in the actual present: there exist only things in the sense of temporal-spatial-qualitative actual structures, which confirms the close connection between psychological and metaphysical analyses. Thus explained is the foundational role of psychology in metaphysics and ontology, and therefore the often successful attempts by Brentano and his pupils to create psychology laboratories in which theorizing could be flanked by experimental research80.

133Brentano criticised both the materialist and spiritualist conceptions of the soul on the grounds of his thesis of intentional reference, and in particular in the light of his distinction between primary and secondary objects. From two opposite points of view, he maintained, materialism and spiritualism are absolutizations of the relationship between the physical and the mental. As to the theory of psychophysical parallelism in theology, Brentano pointed out that in the modern world this had assumed the guise of either correlativism or the more extreme materialism according to which states of consciousness come so close to cerebral processes that they appear as shadows alongside bodies (Schattentheorie). In other words, according to this theory, even if both processes are real, only physical processes can be considered efficacious or causative. A position of this kind obviously conflicted with Brentano’s theory of inner perception, which considered mental phenomena to be activities of functioning. To be rejected as a consequence, according to Brentano, was the form of the materialism of the subject which identified the bearer of mental phenomena with the brain. An analogous and complementary error was committed by spiritualism, which considered the subject to be a spiritual substance because inner perception does not permit the localization of states of awareness81.

134In Brentano’s words:

One view very widely accepted by natural scientists is that a physiological process is the substratum for a psychological one. Consciousness supervenes on certain processes in the brain, so to speak, as a parergon, as a surplus with no corresponding surplus on the other side.
The spiritualists see the matter differently. They imagine every conscious occurrence as something passively accepted, an effect of a physical influence on the soul. And on the other hand they see physical events (e.g., the movement of a limb at will) as caused by psychic influence. Here it would be plausible that there is constant interaction, though perhaps it is not strictly proved.82

135Also in his analysis of religious questions from a philosophical point of view, Brentano again argued consistently with the tenets of his descriptive psychology. Brentano’s position –also on the basis of his analysis of continua and his mereological theory of the act of presentation – was that whatever is apprehended in actual inner perception is neither a spiritual substance nor a material substance; rather, it is a thing (ein Ding), or better a knowing, a feeling, a thinking of some kind, unitary and multiform at the same time. This is not a case of the parts of a whole whereby, for example, corresponding to different perceptual acts (auditory, tactile or visual) located in different parts of the brain are three or more ‘subjects’ or three or more ‘individuals’. As a consequence, there is no point-to-point correspondence between the cerebral mass and conceptual space.

136The soul, or the subject of psychic states, is a zero-dimensional substance within a universe that does not restrict itself to three dimensions but in principle admits to the existence of multi-dimensional topoids. Brentano’s theory thus seems to embrace a pluralistic conception of the universe, although it is one that starts from an immanentist realist foundation of its apperception in intentional reference83.

137It is this feature that links the Brentanists with the contemporary researchers (psychologists, philosophers, logicians, information technologists, neurophysiologists) in the cognitive sciences still working on a theory of the soul in an endeavour to resolve the problem of the relation between mind and body84.

138In fact, despite the enormous development of psychophysics, which since the critique brought against Fechner’s classical version of it has highlighted the importance of qualitative analyses and the existence of various kinds of sensory continua, still unresolved is the problem of identifying the invariants transposed in perception and representation from the environment to the perceiver, as well as the problem of the nature of the information processed by the inner representation. In other words, the problems raised by Brentano in his empirical psychology, and in the substantially Aristotelian terms in which they were couched, still await solution in contemporary science.