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following on one another we perceive the fact of number: and at the same time again as we feel a surface hard or soft we perceive it as some kind of figure. Beyond then the particular objects of the single senses, we require to recognise a number of qualities ('categories' we should call them in modern phraseology) which enter more or less into each of our sensations-" which," in Aristotle's words, "we perceive immediately in connection with each perception." These common objects of perception (aloonτà xoiva) are variously enumerated. Sometimes five are mentioned-movement, rest, number, figure, magnitude: at other times unity as a species of number is added: but there is one passage in which time is appended, and in the Treatise on Sense the common objects of perception are extended so as even to include the rough and smooth, the sharp and blunt'.
Movement is generally regarded as the chief among these common sensibles. The rest may be viewed in fact as, in some way or other, modifications of it. Thus, for example, rest is known by absence of movement, and number is perceived by the negation of what is continuous. Evidently, therefore, since this movement is itself not the product of any one sense but the result of sight and touch in combination, the common objects of perception cannot be referred to any one single organ of particular sensation. For, Aristotle argues, if these common qualities were thus apprehended by any single sense they could be so only in the way in which the perception of some colour gives us the perception of sweet-i.e. because we have perceived the two together at some time in our past experience, and thus in the perception of the one are reminded simultaneously of the other: or else they must be a mere incidental addition to sensation in the way that from a sensation of something white we come to perceive an individual-'the son of Diares,' as the subject of which white was a property. But, Aristotle continues, the common objects of sensation are the
1 De Sens. c. 4, 442h4. De An. 11. 6, 418a17.
result of a common general sense, and not any merely incidental appendage to our sensations: they therefore cannot be regarded as a mere concomitant or ovμßeßŋêòs of sensation. Nor even were they to be apprehended as in the former of our two alternatives, would they even then be classed among the acts of some particular sense-faculty. For to perceive as there described the object of one sense through the perception of another sense really requires a unity of sense: the senses perceive that two qualities are united in one object-e.g. yellow and bitter—not in their own isolated character, but as a combined faculty (oux i αὐταί, ἀλλ ̓ ᾗ μία) and therefore the common sensibles cannot be the product of any special organ of sense'. Rather, in fact, these universal characteristics of all objects of sensation are provided by the central faculty of sense: sight and other senses may contribute largely to a knowledge of them, but in the last resort it is the common sense, the primary source of all sensation, which presents them to our observation.
2. The Consciousness of Sensation.
This comparison of separate sensations in which as we have seen lies the chief action of the central sense involves immediately another property. To judge of two sensations we require a power of holding them before the mind, a power of knowing them as our sensations-a power which transcends the mere sensation of a colour or of a smell as such and recognises it as something belonging to ourselves. What then is this faculty by which we perceive that we perceive-by which we not only see and hear, but perceive that we see and hear? It must, Aristotle holds, be the primary fundamental faculty of all perception-that same central sense which we have previously recognised. For, he reasons, this consciousness of sight (for instance) must be the
1 De An. III. 1. 425a30.
? De Ment. 1. 450312, φανερὸν ὅτι τῷ πρώτῳ αἰσθητικῷ τούτων ἡ γνῶσις ἐστίν. Aristotle specially argues that those common sensibles are a result of sensation and not of thought, because memory involves time (ὅταν ἐνεργῇ τῇ μνήμῃ προσαισθάνεται ὅτι πρότερον).
result either of sight itself or of some sense different from this. But, if we assume the latter, then since the sense which perceives sight also perceives its object, we shall have two sensessight and the sense perceiving sight-relating to one and the same object. This however, Aristotle implies, is absurd, since in this case the one sense would be quite superfluous. It follows therefore that this consciousness of sight is a result of sight itself1. But the sight here mentioned is not the immediate organ of vision. For, Aristotle continues, were the sense which thus perceives the sensation of sight something different from sight itself, the process would either go on to infinity because this sense-perceiving sense would itself require another to perceive it, or else we must at last assume a sense which is itself conscious of its own perception. And this, he adds, we must regard as belonging to the original perceptive faculty (ἐπὶ τῆς πρώτης τοῦτο ποιητέον).
This reference of the consciousness of sensation to that primary power of sense-perception on which all the special senses in some degree depend, is expressed still more clearly in a passage in the Tract on Sleep. "There is," it is there said, "a common power which accompanies all the special senses, and by which the mind perceives both that it sees and that it hears: since it is not by sight it sees that it sees." Unless in fact we are prepared to credit Aristotle with a wonderful amount of inconsistency we must regard the one passage as illustrative of the other. So taking them we cannot but allow that if Aristotle asserts in the one passage "it is not by sight mind sees that it sees," and in the other passage writes "sight perceives that it perceives," he is using sight in the former passage as the mere particular organ, whereas in the other it is identified with that original faculty of sense which serves as basis to the whole system of the senses. The consciousness of sense-perception is then, we may conclude, an attribute of that same central sense
1 De An. III. 2.
2 De Somno 2, 45515.
which enabled us to compare and distinguish the different reports transmitted by our isolated senses. The two functions are in fact but different aspects of one and the same process: for the comparison of the reports of sense involves as its presupposition the conscious recognition of them as our own, the faculty, in other words, of holding them before the mind.
This central sense is thus the basis of our whole perceptive capacity; it is the beginning and the principle of all sensation (apxn τns aio Onoews). But, further, just as each one of the senses has its physical counterpart or organ; and as the soul or yuxí itself is not independent of the body; so in the same way the central sense is regarded as connected with a portion of our body. It might have been supposed that this physical organ of perception would have been the brain, as Aristotle's predecessors had believed. But, Aristotle expresses himself strongly against the view which would connect sense-perception with the cerebral machinery. The brain, he says distinctly in the Treatise on the Parts of Animals, is not the cause of our perceptions, seeing that it is devoid of sensation and is itself but like many of the superfluous discharges'. Particularly does he call attention to the fact that the brain produces no sensation on being touched2. A superficial reader of the Tract on Sense might indeed suppose that the brain is supposed to be essentially connected with the sense of sight. But the three 'passages' which lead from the brain to the eye have nothing to do with the completion of the
1 De Part. An. II. 1o, 636*16, ευαισθησίας ἕνεκεν ἄσαρκον εἶναί φασιν· αἰσθάνεσθαι μὲν γὰρ τῷ ἐγκεφάλῳ, τὴν δ' αἴσθησιν οὐ προσίεσθαι τὰ μόρια τὰ σαρκώδη λίαν· τούτων δ' οὐδέτερόν ἐστιν ἀληθές......τῶν τ' αἰσθήσεων οὐκ αἴτιος οὐδεμιᾶς, ὅς γε ἀναίσθητος καὶ αὐτός ἐστιν ὥσπερ ὁτιοῦν τῶν περιττωμάτων, ἀλλ' οὐχ εὑρίσκοντες διὰ τίνα αἰτίαν ἔνιαι τῶν αἰσθήσεων ἐν τῇ κεφαλῇ τοῖς ζῴοις εἰσὶ, τοῦτο δ' ὁρῶντες ἰδιαίτερον ὂν τῶν ἄλλων μορίων ἐκ συλλογισμοῦ πρὸς ἄλληλα συνδυάζουσιν. ὅτι μὲν οὖν ἀρχὴ τῶν αἰσθήσεών ἐστιν ὁ περὶ τὴν καρδίαν τύπος, διώρισται πρότερον ἐν τοῖς περὶ αἰσθήσεως. Cf. Plato, Timaus 76 B. For Aristotle's misconceptions as to the nature of the brain, see Ogle's note on the passage (Parts of Animals, p. 174).
: De Part. An. 11. 7, 63152, ὅτι μὲν οὖν οὐκ ἔχει συνέχειαν οὐδεμίαν πρὸς τὰ αἰσθητικὰ μόρια, δῆλον μὲν καὶ διὰ τῆς ὄψεως, ἔτι δὲ μᾶλλον τῷ μηδεμίαν ποιεῖν αἴσθησιν θιγγανόμενος, ὥσπερ οὐδὲ τὸ αἷμα οὐδὲ τὸ περίττωμα τῶν ζῴων.
perceptive act: they simply, as has been already pointed out, conduct from the brain that aqueous humour which is employed to receive the object of sensation. The brain in short stands in no real connection with the work of sense-perception, but is viewed simply as serving as a cooling apparatus to counteract the excessive warmth of the heart',
The heart then rather than the brain is the organ in which Aristotle holds the central faculty of sense to be located. By its very position alone the heart is well adapted to discharge the duties of a central sense: placed midway between the front and back it is the natural meeting-place of all the different reports of sense. Nor indeed is it only of the operations of perception that the heart is thus the central principle: it is the centre also of the faculties of growth and reproduction. The heart may therefore be regarded in the Aristotelian System as the physical basis, the physiological counterpart of mind. But it would be a mistake, as Neuhäuser has fully pointed out, to identify the central sense, the original faculty of the perceptive act, with the heart which Aristotle thus describes. True indeed if we confined our observations simply to the physical and physiological treatises of Aristotle we could hardly but conclude that Aristotle views the heart as actually the organ which effects that comparison and distinction of sensations which we have before described. But, it should be noticed, Aristotle nowhere says that this central common faculty of sense-perception is itself
1 De Part. An. II. 7, 632510, ἐπεὶ δὲ ἅπαντα δεῖται τῆς ἐναντίας ῥοπῆς ἵνα τυγχάνῃ τοῦ μετρίου καὶ τοῦ μέσου, διὰ ταύτην τὴν αἰτίαν πρὸς τὸν τῆς καρδίας τόπον καὶ τὴν ἐν αὐτῇ θερμότητα μεμηχάνηται τὸν ἐγκέφαλον ἡ φύσις.
3 De furent. 3, 46gro, ἀλλὰ μὴν τό γε κύριον τῶν αἰσθήσεων ἐν ταύτῃ (τῇ καρδίᾳ) τοῖς ἐναίμοις πᾶσιν· ἐν τούτῳ γὰρ ἀναγκαῖον εἶναι τὸ πάντων τῶν αἰσθητηρίων κοινὸν αἰσθητήριον.
De Gen. Αn. 11. 6, 743515, διὰ μὲν οὖν τὸ τὴν ἀρχὴν ἐν τῇ καρδίᾳ τῶν αἰσθή· σεων εἶναι καὶ τοῦ ζῴου παντὸς αὕτη γίνεται πρῶτον.
3 De Juvent. 1, 461528, ἐπεὶ οὖν τῶν ἰδίων αἰσθητηρίων ἔν τι κοινόν ἐστιν αἰσθητήριον, εἰς ὃ τὰς κατ' ἐνέργειαν αἰσθήσεις ἀναγκαῖον ἁπαντῶν, τοῦτο δ' ἂν εἴη μέσον τοῦ πρόσθεν καλουμένου καὶ ὄπισθεν.
4 469-6: 4695.
Aristoteles' Lehre von dem sinnlichen Erkenntnissvermögen.