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CHAPTER III: THAT EVERY AGENT ACTS FOR A GOOD
HENCE we must go on to prove that every agent acts for a good.
For that every agent acts for an end clearly follows from the fact that every agent tends to something definite. Now that to which an agent tends definitely must needs be befitting to that agent: since the latter would not tend to it save on account of some fittingness thereto. But that which is befitting to a thing is good for it. Therefore every agent acts for a good.
Further. The end is that wherein the appetite of the agent or mover is at rest, as also the appetite of that which is moved. Now it is the very notion of good to be the term of appetite, since good is the object of every appetite. Therefore all action and movement is for a good.
Again. All action and movement would seem to be directed in some way to being: either for the preservation of being in the species or in the individual; or for the acquisition of being. Now this itself, being to wit, is a good: and for this reason all things desire being. Therefore all action and movement is for a good.
Furthermore. All action and movement is for some perfection. For if the action itself be the end, it is clearly a second perfection of the agent. And if the action consist in the transformation of external matter, clearly the mover intends to induce some perfection into the thing moved: towards which perfection the movable tends, if the movement be natural. Now when we say a thing is perfect, we mean that it is good. Therefore every action and movement is for a good.
Also. Every agent acts according as it is actual. Now by acting it tends to something similar to itself. Therefore it tends to an act. But an act has the ratio of good: since evil is not found save in a potentiality lacking act. Therefore every action is for a good.
Moreover. The intellectual agent acts for an end, as determining on its end: whereas the natural agent, though it acts for an end, as proved above, does not determine on its end, since it knows not the ratio of end, but is moved to the end determined for it by another. Now an intellectual agent does not determine the end for itself except under the aspect of good; for the intelligible object does not move except it be considered as a good, which is the object of the will. Therefore also the natural agent is not moved, nor does it act for an end, except in so far as this end is a good, since the end is determined for the natural agent by an appetite. Therefore every agent acts for a good.
Again. To shun evil and to seek good are in the same ratio: even as movement from below and upward movement are in the same ratio. Now we observe that all things shun evil: for intellectual agents shun a thing for the reason that they apprehend it as an evil: and all natural agents, in proportion to their strength, resist corruption which is the evil of everything. Therefore all things act for a good.
Again. That which results from the agent's action beside his intention, is said to happen by chance or luck. Now we observe in the works of nature that either always or more often that happens which is best: thus in plants the leaves are so placed as to protect the fruit; and the parts of an animal are so disposed as to conduce to the animal's safety. Wherefore, if this happens beside the intention of the natural agent, it will be the result of chance or luck. But that is impossible: because things that happen always or frequently, are not casual or fortuitous, but those which occur seldom. Therefore the natural agent tends to that which is best: and much more evidently is this so with the intellectual agent. Therefore every agent intends a good in acting.
Moreover. Whatever is moved is brought to the term of movement by the mover and agent. Therefore mover and moved tend to the same term. Now that which is moved, since it is in potentiality, tends to an act, and consequently to perfection and goodness: for by its movement it passes from potentiality to act. Therefore mover and agent by moving and acting always intend a good.
Hence the philosophers in defining the good said: The good is the object of every appetite; and Dionysius (De Div. Nom. iv.) says that all things desire the good and the best.
|Source: St. Thomas Aquinas, The Summa Contra Gentiles, trans. by The English Dominican Fathers from the latest Leonine Edition, Benzinger Brothers: New York, 1924.|