Exposition of the Faith

We hold, therefore, that free-will comes on the scene at the same moment as reason, and that change and alteration are congenital to all that is produced. For all that is produced is also subject to change. For those things must be subject to change whose production has its origin in change. And change consists in being brought into being out of nothing, and in transforming a substratum of matter into something different. Inanimate things, then, and things without reason undergo the aforementioned bodily changes, while the changes of things endowed with reason depend on choice. For reason consists of a speculative and a practical part. The speculative part is the contemplation of the nature of things, and the practical consists in deliberation and defines the true reason for what is to be done. The speculative side is called mind or wisdom, and the practical side is called reason or prudence. Every one, then, who deliberates does so in the belief that the choice of what is to be done lies in his hands, that he may choose what seems best as the result of his deliberation, and having chosen may act upon it. And if this is so, free-will must necessarily be very closely related to reason. For either man is an irrational being, or, if he is rational, he is master of his acts and endowed with free-will. Hence also creatures without reason do not enjoy free-will: for nature leads them rather than they nature, and so they do not oppose the natural appetite, but as soon as their appetite longs after anything they rush headlong after it. But man, being rational, leads nature rather than nature him, and so when he desires anything he has the power to curb his appetite or to indulge it as he pleases. Hence also creatures devoid of reason are the subjects neither of praise nor blame, while man is the subject of both praise and blame.

Note also that the angels, being rational, are endowed with free-will, and, inasmuch as they are created, are liable to change. This in fact is made plain by the devil who, although made good by the Creator, became of his own free-will the inventor of evil, and by the powers who revolted with him, that is the demons, and by the other troops of angels who abode in goodness.