Thomas Aquinas

“ But every act of choosing is in regard to something that seems in some way better. Therefore every choice is made necessarily.
On the contrary, Choice is an act of a rational power; which according to the Philosopher (Metaph. ix, 2) stands in relation to opposites.
I answer that, Man does not choose of necessity. And this is because that which is possible not to be, is not of necessity. Now the reason why it is possible not to choose, or to choose, may be gathered from a twofold power in man. For man can will and not will, act and not act ”

“ Therefore the impossible is not the object of choice.
Reply to Objection 1: The will stands between the intellect and the external action: for the intellect proposes to the will its object, and the will causes the external action. Hence the principle of the movement in the will is to be found in the intellect, which apprehends something under the universal notion of good: but the term or perfection of the will's act is to be observed in its relation to the action whereby a man tends to the attainment of a thing; for the movement of the will is from the soul to the thing. ”

“ If two things be proposed as equal under one aspect, nothing hinders us from considering in one of them some particular point of superiority, so that the will has a bent towards that one rather than towards the other. ”

“ But irrational animals desire something on account of an end: since they act for an end, and from desire. Therefore choice is in irrational animals.
Objection 2: Further, the very word "electio" [choice] seems to signify the taking of something in preference to others. But irrational animals take something in preference to others: thus we can easily see for ourselves that a sheep will eat one grass and refuse another. Therefore choice is in irrational animals.
Objection 3: Further, according to Ethic. vi, 12, "it is from prudence that a man makes a good choice of means." ”

“ The perfect good alone, which is Happiness, cannot be apprehended by the reason as an evil, or as lacking in any way. Consequently man wills Happiness of necessity, nor can he will not to be happy, or to be unhappy. Now since choice is not of the end, but of the means, as stated above (A [3] ) ; it is not of the perfect good, which is Happiness, but of other particular goods. Therefore man chooses not of necessity, but freely.
Reply to Objection 1: The conclusion does not always of necessity follow from the principles, but only when the principles cannot be true if the conclusion is not true. ”

“ Wherefore an end cannot be possible, unless the means be possible. Now no one is moved to the impossible. Consequently no one would tend to the end, save for the fact that the means appear to be possible. ”

“ Therefore choice is not concerned with human acts alone.
Objection 3: Further, men are chosen for certain posts, whether secular or ecclesiastical, by those who exercise no action in their regard. Therefore choice is not concerned with human acts alone. ”

“ The same may be seen in the movements of clocks and all engines put together by the art of man. Now as artificial things are in comparison to human art, so are all natural things in comparison to the Divine art. And accordingly order is to be seen in things moved by nature, just as in things moved by reason, as is stated in Phys. ”