Thomas Aquinas

“ Now in us the principle of an act is both power and habit; for we say that we know something both by knowledge and by the intellectual power. Therefore free-will must be either a power or a habit, or a power with a habit. That it is neither a habit nor a power together with a habit, can be clearly proved in two ways. First of all, because, if it is a habit, it must be a natural habit; for it is natural to man to have a free-will. ”

“ The adventitious qualities are habits and passions, by virtue of which a man is inclined to one thing rather than to another. And yet even these inclinations are subject to the judgment of reason. Such qualities, too, are subject to reason, as it is in our power either to acquire them, whether by causing them or disposing ourselves to them, or to reject them. And so there is nothing in this that is repugnant to free-will. ”

“ Faculty sometimes denominates a power ready for operation, and in this sense faculty is used in the definition of free-will. But Bernard takes habit, not as divided against power, but as signifying a certain aptitude by which a man has some sort of relation to an act. And this may be both by a power and by a habit: for by a power man is, as it were, empowered to do the action, and by the habit he is apt to act well or ill. ”

“ For the sheep, seeing the wolf, judges it a thing to be shunned, from a natural and not a free judgment, because it judges, not from reason, but from natural instinct. And the same thing is to be said of any judgment of brute animals. But man acts from judgment, because by his apprehensive power he judges that something should be avoided or sought. But because this judgment, in the case of some particular act, is not from a natural instinct, but from some act of comparison in the reason, therefore he acts from free judgment and retains the power of being inclined to various things. ”

“ Now, in matters of knowledge, the principles are related to the conclusion to which we assent on account of the principles: just as, in appetitive matters, the end is related to the means, which is desired on account of the end. Wherefore it is evident that as the intellect is to reason, so is the will to the power of choice, which is free-will. ”

“ But the free-will is indifferent to good and evil choice: wherefore it is impossible for free-will to be a habit. Therefore it is a power.
Reply to Objection 1: It is not unusual for a power to be named from its act. And so from this act, which is a free judgment, is named the power which is the principle of this act. Otherwise, if free-will denominated an act, it would not always remain in man. ”

“ Now particular operations are contingent, and therefore in such matters the judgment of reason may follow opposite courses, and is not determinate to one. And forasmuch as man is rational is it necessary that man have a free-will. ”

“ But on the part of the body and its powers man may be such by virtue of a natural quality, inasmuch as he is of such a temperament or disposition due to any impression whatever produced by corporeal causes, which cannot affect the intellectual part, since it is not the act of a corporeal organ. ”