Article 3 — Whether the appetite is a special power of the soul

Third, it is asked whether the appetite is a special power of the soul. (Parallel texts: ST I.80.1; In III Sent., d. 27, q. 1, a. 2.)

Obj. 1: It seems that it is not. For powers of the soul are only ordered to vital activities. But vital activities are what distinguish the ensouled from the unensouled. But the ensouled are not distinguished from the unensouled with regard to desire, for the unensouled also desire goodness. Therefore, appetite is not a special power of the soul.

Obj. 2: Furthermore, appetite seems to be nothing else than a certain direction toward an end. But natural appetite is sufficient for something to be directed by it to an end. Therefore, one must not adjoin the animal appetite, which is a special power of the soul.

Obj. 3: Furthermore, activities and powers differ with regard to their limits. But the limit of both the natural and animal appetite is the same, that is, goodness. Therefore, it is the same power or activity. But natural appetite is not a power of the soul. Therefore, neither is the animal appetite.

Obj. 4: Furthermore, appetite pertains to a thing that is not possessed, according to Augustine. (Augustine, On the Trinity, bk. 9, ch. 12 (PL 42:971); cf. Enarrationes in Psalmos on Psalm 118:20, sermon 8, para. 5 (PL 37:1522).) But goodness, moreover, is possessed by knowledge. Therefore, among animals, a certain appetite, which requires a special power, does not follow upon the knowledge of goodness.

Obj. 5: Furthermore, a special power is ordered to a special act, however, not to an act common to all the powers of the soul. But to desire goodness is common to all the soul's powers, which is clear from the fact that any power whatsoever desires its own object and delights in it. Therefore, appetite is not a special power of the soul.

Obj. 6: Furthermore, if an appetitive power desires goodness, it either desires goodness commonly, or else goodness for itself. However, if it should desire goodness commonly, since every other power desires a particular good, the appetitive power will not be a special power, but a universal one. However, if it should desire goodness for itself, since any other power also desires goodness for itself, any other power could be called an appetite for the same reason. Therefore, there will not be a power which ought to be specially called appetite.

On the contrary is what the Philosopher posits in On the Soul, (Aristotle, On the Soul 3.15, 433a31. See also De anima 2.5, 414a31.) that the appetitive is a special power of the soul.

I answer that it must be said that the appetite is a special power of the soul. In evidence of this it must be known that when powers of the soul are ordered to activities which are proper to ensouled things, in this respect, some activities are such that a special power of the soul is assigned to them, so that it is itself the proper activity of the soul. However, one can find an activity of the soul which in one way is common to both ensouled and unensouled things, but in another way is proper to ensouled things, as being moved and being begotten. For spiritual things absolutely possess a nature such as to move others, but not so as to be moved. However, bodily things are moved, and even though one can move another, yet none of them can move itself. For, as is proved in the Physics, (Aristotle, Physics 8.10, 257a33.) whatever moves itself is divided into two parts, one of which is the mover and the other is the moved.

But this cannot be the case in entirely bodily things, for their forms cannot be movers, even though they can be a beginning of motion, as that by which something is moved. For example, in the motion of the earth, weight is the beginning by which it is moved, yet it is not the mover. And this happens both on account of the simplicity of unensouled bodily things, which do not have enough diversity in their parts such that one part can be the mover and another be the moved, and also on account of the baseness and materiality of the forms. For since they are very distant from the separated forms, to which it belongs to move, they do not retain the capacity of being able to move, but only of being the beginnings of motion.

However, unensouled things are composed of a spiritual and bodily nature, hence one part cannot be moving in them and another be moved, whether with respect to local motion or other kinds of motion. And thus, inasmuch as the proper action of ensouled things themselves is made to be moved, such that they move themselves to determinate species of motion: special ordered powers are found within animals, such as the motive power in animals for local motion, the augmentative power commonly within plants and animals for the motion of growth, the nutritive power for the motion of alteration, and the generative power for the motion of generation. Similarly desire, which is somehow common to all things, belongs to ensouled things in a special way, that is, to animals inasmuch as there is within them an appetite and something moving the appetite, according to the Philosopher in On the Soul. (Aristotle, On the Soul 3.15, 433b11.) Hence, just as animals are moved by themselves more than others, so also do they desire by themselves. And because of this, just as the motive power is a special power within the soul, so also is the appetitive power.

Reply Obj. 1: To the first, therefore, the solution is clear from what has already been said.

Reply Obj. 2: To the second it must be said that since animals are made such as to participate in divine goodness more eminently than other lower things, it is for this reason that they need more activities and helps for their own perfection, just as one who can attain perfect health with much exercise is closer to health than one who can only attain a little health and who only needs a little exercise for this, according to the example of the Philosopher in On the Heavens. (Aristotle, On Heaven 2.18, 292a22.) And thus, since the natural appetite is determined to one thing (it cannot be multiform, so as to extend to as many different things as animals might need), it was necessary that there should be added to animals an appetite following upon apprehension, so that from the multitude of things apprehended, an animal could be carried toward different things.

Reply Obj. 3: To the third it must be said that, even though goodness is desired by the natural appetite as by the animal appetite, nevertheless, something does not desire goodness by natural appetite on its own, as it does by the animal appetite. And thus, in order to desire goodness, a power is needed for the animal appetite which is not necessary for desiring by the natural appetite. And furthermore, the good to which natural appetite tends is determinate and uniform, but this is not the case with regard to the good desired by the animal appetite. And one can draw a similar conclusion with regard to the motive power.

Reply Obj. 4: To the fourth it must be said that one desiring goodness does not seek to possess goodness with regard to intentional being, as it is possessed by the one who knows, but rather with regard to natural being. And thus, inasmuch as the animal possesses goodness as knowing it, nothing prevents it from being able to desire it.

Reply Obj. 5: To the fifth it must be said that each power desires its object with a natural desire. But the animal desire pertains to a special power. And since the natural desire is determined to one thing, yet the animal follows after its apprehension, hence each power desires a determinate good, whereas the appetitive power desires any apprehended good. But it does not follow that it is a general power, since it desires common goodness in a particular way.

Reply Obj. 6: Hence, the answer to the final objection is also clear.