Summa contra Gentiles3.2 Chapter II. That every agent acts for an end

action, intends an end. For in those things which clearly act for an end, we declare tends: for when this is reached, the end is said to be reached, and to fail in this is to fail in the end intended; as may be seen in the physician who aims at health, and in a man who runs towards an appointed goal. Nor does it matter, as to this, whether that which tends to an end be cognitive or not: for just as the target is the end of the archer, so is it the end of the arrow’s flight. Now the movement of every agent tends to something determinate: since it is not from any force that any action proceeds, but heating proceeds from heat, and cooling from cold; wherefore actions are differentiated by their active principles. Action sometimes terminates in something made, for instance building terminates in a house, healing ends in health: while sometimes it does not so terminate, for instance, understanding and sensation. And if action terminate in something made, the movement of the agent tends by that action towards that thing made: while if it does not terminate in something made, the movement of the agent tends to the action itself. It follows therefore that every agent intends an end while acting, which end is sometimes the action itself, sometimes a thing made by the action.

Again. In all things that act for an end, that is said to be the last end, beyond which the agent seeks nothing further: thus the physician’s action goes as far as health, and this being attained, his efforts cease. But in the action of every agent, a point can be reached beyond which the agent does not desire to go; else actions would tend to infinity, which is impossible, for since it 7s not possible to pass through an infinite medium,’ the agent would never begin to act, because nothing moves towards what it cannot reach. Therefore every agent acts for an end.

Moreover. If the actions of an agent proceed to infinity, these actions must needs result either in something made, or not. If the result is something made, the being of that thing made will follow after an infinity of actions. But that which presupposes an infinity of things, cannot possibly be, since an infinite mediwm cannot be passed through." Now impossibility of being argues impossibility of becoming:

and that which cannot become, it is impossible to make. Therefore it is impossible for an agent to begin to make a thing for the making of which an infinity of actions are pre-supposed.—If, however, the result of such actions be not something made, the order of these actions must be either according to the order of active forces, (for instance if a man feel that he may imagine, and imagine that he may understand, and understand that he may will): or according to the order of objects, (for instance I consider the body that I may consider the soul, which I consider in order to consider a separate substance, which again I consider so that I may consider God). Now it is not possible to proceed to infinity, either in active forces, as neither is this possible in the forms of things, as proved in 2 Metaph., since the form is the principle of activity: or in objects, as neither is this possible in beings, since there is one first being, as we have proved above. Therefore it is not possible for agents to proceed to infinity: and consequently there must be something, which being attained, the efforts of the agent cease. Therefore every agent acts for an end.

Further. In things that act for an end, whatsoever comes between the first agent and the last end, is an end in respect to what precedes, and an active principle in respect of what follows. Hence if the effort of the agent does not tend to something determinate, and if its action, as stated, proceeds to infinity, the active principles must needs proceed to infinity: which is impossible, as we have shown above. Therefore the effort of the agent must of necessity tend to something determinate.

Again. Every agent acts either by nature or by intelligence. Now there can be no doubt that those which act by intelligence act for an end; since they act with an intellectual preconception of what they attain by their action, and act through such preconception, for this is to act by intelligence. Now just as in the preconceiving intellect by the action of the intellectual being, so in the natural 1 Bk. I, ch. xlii.

agent there pre-exists the similitude of the natural effect, by virtue of which similitude its action is determined to the appointed effect: for fire begets fire, and an olive produces an olive. Wherefore even as that which acts by intelligence tends by its action to a definite end, so also does that which acts by nature. Therefore every agent acts for an end.

Moreover. Fault is not found save in those things which are for an end: for we do not find fault with one who fails in that to which he is not appointed; thus we find fault with a physician if he fail to heal, but not with a builder or a grammarian. But we find fault in things done according to art, as when a grammarian fails to speak correctly; and in things that are ruled by nature, as in the case of monstrosities. Therefore every agent, whether according to nature, or according to art, or acting of set purpose, acts for an end.

Again. Were an agent not to act for a definite effect, all effects would be indifferent to it. Now that which is indifferent to many effects does not produce one rather than another: wherefore from that which is indifferent to either of two effects, no effect results, unless it be determined by something to one of them. Hence it would be impossible—for it to act. Therefore every agent tends to some definite effect, which is called its end.

There are, however, certain actions which would seem not to be for an end, such as playful and contemplative actions, and those which are done without attention, such as scratching one’s beard, and the like: whence some might be led to think that there is an agent that acts not for an end.—But we must observe that contemplative actions are not for another end, but are themselves an end. Playful actions are sometimes an end, when one plays for the mere pleasure of play; and sometimes they are for an end, as when we play that afterwards we may study better. Actions done without attention do not proceed from the intellect, but from some sudden act of the imagination, or some natural principle: thus a disordered humour produces an itching sensation and is the cause of a man scratching his beard, which he does without his mind attending toit. Such actions do tend to an end, although outside the order of the intellect. Hereby is excluded the error of certain natural philosophers of old, who maintained that all things happen by natural necessity, thus utterly banishing the final cause from things.