§ 836. The Philosopher now passes from a general consideration of the principle of local movement in itself to viewing it in relation to different types of animal. And he does three things here. First, he states what is common to all animals that move; then, at 'Now we must consider', he discusses the motive-principle of imperfect animals; and thirdly, at 'Sensitive imagination', that of the most perfect animal, man, in whom this principle exists in a unique way.
First, then, he observes that all animals have the power of self-movement inasmuch as they have appetition; for appetition is precisely the cause of movement. Now appetition connotes imagination, either rational or merely sensuous; and while the latter is found in other animals, the former is proper to man alone.
§ 837. Note, however, that, just as Aristotle has included imagination under the term 'intellect', so now he extends the term 'imagination' to denote something intellectual; and in this he is guided by the meaning of the term itself. For imagination is a sort of appearance; and things 'appear' to both sense and intellect. Besides, imagination can function, like reason or intellect, in the absence of exterior sense-objects.
§ 838. Then, at 'Now we must consider', he points to the motive-principle in imperfect animals, that is, in those which have no sense but touch. We must ask, he says, what it is that moves these animals: can it be imagination and desire? They seem indeed to have desires, for they seem to feel joy and displeasure: they shrink back when touched by things that trouble them, but open out and extend themselves towards things that suit them, which implies a sense of pain and pleasure. And this in turn implies desire. And since desire springs from a sense of pleasure it must involve some kind of image-representation.
§ 839. But of what kind is this? An answer, he says, may be gleaned from considering the movements of these animals. They do not move as with a definite end in view, as if intending to arrive at any particular spot, as do the animals that move from one place to another and that form an inward image of things at a distance, and so desire these things and move towards them. The imperfect animals form images only of objects actually present to their exterior sense--not of things at a distance. When they are hurt the image which they form conveys to them the exterior object as harmful, and thus they shrink from it. And as soon as anything affords them pleasure they reach out to it and cling to it. Thus both imagination and desire in them are indefinite, in the sense that they form images which warn or attract them without being images of any distinct thing in this or that definite place. They have a confused imagination and desire.
§ 840. Next, at 'Sensitive imagination', he points out the motive-principle in man; and this in three stages. He shows first how this principle is the deliberative reason; next, at 'Appetite sometimes overcomes', how it is sometimes overcome by desire; and thirdly, at 'The cognitive faculty', of what 'reason' he is speaking here. First, then, he says that while sensuous imagination exists also in other animals, deliberative imagination is proper to rational ones; to deliberate, that is to weigh alternatives, is a function of reason.
§ 841. And this deliberation requires some sort of rule or end by which to reckon what most needs to be done. Clearly, a man will 'follow', i.e. seek for, the better and more suitable alternative: which is always measured by some standard. We need therefore a measure for our actions, a criterion for discerning what is most worth doing. And this will be the middle term of the syllogism of the practical reason issuing in a choice. It follows that reason, deliberating, can form several images into a unity--three, to be precise; for one object is preferred to another, and a third gives the standard of preference.
§ 842. We can see now why animals form no opinions, though they have images. They cannot prefer one thing to another by any process of reasoning. Rational deliberation, however, issues in opinion--else it would not unify a number of phantasms. Similarly, the lower appetite springing from imagination is non-deliberate: it moves at once into desire or repulsion following the sensuous imagination.
§ 843. Next, at 'Appetite sometimes', he explains how rational deliberation may yield to the lower desire, may be overcome by it and drawn away from its own decision. Again, conversely, the superior appetite that follows rational deliberation sometimes sways the lower one that follows sensuous images (as a higher heavenly body may impel a lower). This happens in the case of 'continence'; for the continent are those in whom deliberation gets the better of passion.
§ 844. Note that it is according to nature that the higher appetite should sway the lower. We see this in the heavenly bodies; the higher sphere gives the first impetus, moving the lower which, in turn, has a three-fold local movement. For the sphere, e.g., of Saturn moves first in diurnal motion, turning about the poles of the Universe; then in the contrary zodiacal motion; and thirdly, in its own proper motion. Likewise, the lower appetite, retaining something of its own proper movement, is also moved by another, and this naturally, following the impulse of the higher appetite and of rational deliberation. If the converse takes place, and the higher is in fact moved by the lower, this is contrary to the natural order of things.
§ 845. Then, at 'the cognitive faculty', he explains which 'reason' it is that initiates movement. It is not the speculative reason (here called 'cognitive'); for this remains quiet and still and makes no decisions about tending to or away from anything, as we have seen. And as for the practical reason, it is either universal or particular. By the universal practical reason we judge that such and such ought to be done, e.g. that children ought to honour their parents. By the particular practical reason we judge that this particular subject is such and such, e.g. that I am a son and I ought here and now to honour my parents.
§ 846. Now it is this latter judgement that moves to action, not the other universal one;--or, if both move, the universal moves as a first and motionless cause of movement, the particular as a proximate cause already, to a certain extent, applied to the movement itself. For deeds and movements are in the particular, and if any movement is actually to take place, the universal opinion must be particularised. In the same way the commission of any sinful action implies that one's good judgement as to what should be done in the particular is neutralised by a pleasure or emotion of some kind; one's universal opinion remaining, however, unaltered.
434a 23-435a 10