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(Aristotle further explains) these souls or faculties of soul form an ascending series in which the higher faculty involves and comprehends the lower. The functions of nutrition are the basis for the faculties of sense: and the exercise of sense is necessary to provide a foundation and materials for thought. "The different forms of soul in fact stand to one another in the same way as do the several species of figure: both in the case of figures and of animate beings the earlier forms always exist potentially in the later1." Just in short as the triangle may be regarded as the basis of all other rectilineal figures: so, in like manner, may the nutritive functions be viewed as the presupposition of all the later faculties, so that the possession of the sensitive faculties involves the possession of the faculties of nutrition, while the exercise of reasoning and thought implies and rests upon both the nutrient and sentient capacities.
Two points of view must be however steadily embraced in studying Aristotle's theory of faculties. On the one hand, it must be remembered that no higher exercise of soul can be dissevered from its lower animal presuppositions. But on the other hand we must remember also that each one of these faculties is a faculty of soul, and that it is only by reference to the unity of the soul that each can be rightly understood. Nor must we fail to note the general distinction Aristotle draws between that which is prior in order of time and that which is prior in order of thought. If modern theories of development have often neglected the distinction between 'nature' and 'history,' between the chronological genesis of a phenomenon and its existence as a logical conception, Aristotle repeatedly asserts that the reality precedes the potentiality and that if in time the lower form has the priority, still, in thought and real being, the higher, more developed form always stands the first. And in reading his natural history, as we may call it, of the mind,
1 II. 3, 41428.
we cannot too often recall his own caution against forgetting whether we should describe how each thing naturally comes in existence or how it actually is'.
VI. THE NUTRIENT FUNCTIONS.
The first among these psychic faculties, that viz. which constitutes the basis of vegetable life-need not detain us long. It also, we must remember, is a first entelechy-the implicit perfection of plant life-the cause or principle on which the different phenomena of growth eventually rest. Its work may be reduced to two main functions-those of reproduction and of absorbing food. It stands therefore first among those steps or stages of ideal perfection which Aristotle knows as 'souls.' It is accordingly 'the most common form of the soul:' it is the essential characteristic of all vegetable life and it forms the necessary presupposition of all the higher faculties, because it secures those very conditions of existence without which any further exercise of function is impossible. Its two functions-reproduction and nutrition—are in Aristotle's theory closely connected with one another. The absorption of food is but the beginning of that process which finds its natural termination in the creation of another life. Nature in no one of all her operations acts without an aim or fruitlessly: and the assimilation of nutrition has for its end the permanent continuance of existence. "It is in fact the most natural of functions in every animal to generate another like itself in order that the individual may thus as far as possible participate in the eternal and divine." The character of food itself as nourishment Aristotle takes some trouble to determine. The common opinion he finds is that
1 De Part. 4n. 640*18, δεῖ δὲ μὴ λεληθέναι πότερον προσήκει λέγειν πῶς ἕκαστον γίνεσθαι πέφυκε μᾶλλον ἢ πῶς ἔστιν. ἡ γὰρ γένεσις ἕνεκα τῆς οὐσίας ἐστίν, ἀλλ' οὐχ ἡ οὐσία ἕνεκα τῆς γενέσεως. Metaph. M. 107718, τὸ ἀτελὲς μέγεθος γενέσει μὲν πρότερόν ἐστι, τῇ οὐσίᾳ δ' ὕστερον, οἷον ἄψυχον ἐμψύχου.
contrary is nourished by contrary: but there are others who explain it by the contact of similars. Between these two opinions, Aristotle, in accordance with his usual method, takes up an intermediate position. "So far," he thinks, "as the food is undigested, the contrary is nurtured by the contrary: so far as it is digested the like is nurtured by the like',"-in other words the food becomes assimilated to the organism which it is destined to maintain.
Assimilation is thus the character of the process through which the lowest of the psychic faculties displays its operation. But we shall find that the mode of action thus assigned the nutrient faculties foreshadows as it were the manner in which all the other activities of soul are conceived to act. We may in fact say, with Bäumker, that while the plant assimilates the material in a material manner, sense assimilates the material in an immaterial manner, and thought assimilates the immaterial in an immaterial manner. And if this be more epigrammatic than true, it is at least the case that both in sensation and in thought, the work of soul resolves itself into a "receptive" act which cannot but carry with it many of the assimilating associations of the nutrient activities,
VII. THE FACULTIES OF SENSE.
From the capacities of growth and reproduction, Aristotle passes to the faculties of sense. These sentient capacities mark a decided point in the development of life on earth: for it is the possession of the powers of sense which first constitutes the animal. As the vegetable functions were characteristic of the plant, so it is the attribute of sensation which distinguishes the animal from objects simply animate. There is indeed, as we
1 II. 4, 416° 7.
De Part. An. III. 4, 666a34: Tò Šŵov aio0ńσel pioral. De An. 11. 2. 4, 4132.
have seen, a certain amount of similarity, between the action of the nutrient and the action of the sensitive capacities in dealing with their materials. Both receive or apprehend their object, but the degree to which they do so is intrinsically different. The faculties which constitute plant life simply devour their object, they take in the matter as well as the form of that which they employ as nutriment; whereas the faculties of sense receive nothing but the form of their object while they leave the matter, of which it is composed, untouched'.
Sensation is thus usually explained by Aristotle as a process in which we are 'moved' or 'affected' (literally, 'suffer') by an external object. It involves therefore immediately an 'alteration' or a qualitative transformation: the affection, which is the vehicle of alteration, produces a change in the nature or quality of the organ which perceives. The hand in fact, Aristotle might be taken to imply, becomes, when it perceives something, altered in its quality it loses its own temperature and becomes cold or hot like its object: it is altered or transformed by the external object of sensation. So again the eye in perceiving colour becomes as it were coloured itself: it is subject, that is, to a qualitative change by means of the affection to which it is exposed. But this susceptibility upon the part of sense is not a susceptibility to the actual object of sensation: it is but the specific character, the determining form which the sense receives. And accordingly we find the faculty of sense defined as a power of receiving sensible objects without their material concomitants,
1 II. 12, 42432-42462.
II. 5, 416533: ἡ δ' αἴσθησις ἐν τῷ κινεῖσθαί τε καὶ πάσχειν συμβαίνει· δοκεῖ γὰρ ἀλλοίωσίς τις εἶναι. ἀλλοίωσις itself is regarded as a kind of κίνησις, a μεταβολὴ κατὰ τὸ ποιόν, and more definitely we read De Gen. 1. 4, 319 ro: ἀλλοίωσις μέν ἐστιν ὅταν ὑπομένοντος τοῦ ὑποκειμένου, αἰσθητοῦ ὄντος, μεταβάλλῃ ἐν τοῖς αὐτοῦ πάθεσιν ἢ ἐναντίοις οὖσιν ἢ μεταξύ. That πάθος is the vehicle of ἀλλοίωσις appears from Metaph. Δ. 21, 101115, πάθος λέγεται ἕνα μὲν τρόπον ποιότης καθ ̓ ἣν ἀλλοιοῦσθαι ἐνδέχεται.
3 So in II. 12. 4, 42434, Aristotle asks why plants do not perceive-xal yàp ψύχεται καὶ θερμαίνεται—i.e. they display signs of that ἀλλοίωσις which was said to constitute perception.
4 111. 2, 425022: τὸ ὁς ὢν ἔστιν ὡς κεχρωμάτισται.
just in the same way as the wax receives the figure of the seal without the iron or the gold of which the seal itself may be composed'.
Thus far Aristotle might seem to offer little but a mechanical interpretation of the perceptive powers. It might appear in fact as if sensation were nothing but a physiological process in which external objects stamped themselves upon the corporeal organism and so gave rise to various corresponding perceptions. But Aristotle supplements his theory in such a way as renders such an interpretation indefensible. The passive affection which is involved in all sensation is not merely passive; nay rather we may call it non-passivity. For if suffering (Táσxe) be identical with being moved (kiveîobai), it is virtually equivalent to active energy (èvepyeiv). In receiving as it does the forms of things, sense is more than receptive: at the same time as it is impressed, it also in its turn impresses and gives that eldos to the things of sense without which they could not be otherwise perceived. But the writer fails here, as he fails always, to draw a distinction between the work of sense and the work of thought: and though we learn that the sensitive act (alobáveolai) is limited to an individual ‘here' and 'now,' while perception (alo Onois) refers to the general aspect of a quality (Tolóvde), we are not told how this transition is effected.
The searching analysis to which Aristotle subjects the terms which he himself applies to sense-perception makes it however at least clear that it is only in a limited acceptation that we can describe the faculty of sense either as a mere capacity (dúvaμis) or as merely a 'suffering' or passive affection (πáðos)3. We must remember says Aristotle that 'capacity' and 'affection' are not univocal. A man may possess a 'capacity' of knowledge (for instance) either because he belongs to the class of beings capable of knowledge, or because he possesses an ac
II. 12, 42418: ἡ μὲν αἴσθησίς ἐστι τὸ δεκτικὸν τῶν αἰσθητῶν εἰδῶν ἄνευ τῆς ὕλης, οἷον ὁ κηρὸς τοῦ δακτυλίου ἄνευ τοῦ σιδήρου καὶ τοῦ χρυσοῦ δέχεται τὸ σημεῖον.
2 111. 4, 42929: ἡ ἀπάθεια τοῦ αἰσθητικοῦ.
3 II. 5, 417ab.