That is to say, every subject acts toward an end that is a good for him. Metaphysically speaking, aside from the Divine essence, in all other acting subjects individual human action implies the change from potency to act, and this act implies a gradually increasing perfection of the acting subject. Rational behavior adds to the acting subject's intelligence and free will, so we must talk in this case of an acting person who knows that she is using limited means to achieve ends that are not limited per se. In the case of human action, we must account for the fact that this action is the result of a substantial unity. Aquinas states clearly that human intelligence utilizes the senses even in the process of abstract thought.
Senses are, therefore, instrumental causes within the intellectual process.
In Thomistic philosophical reflection, the passions are not separable from rational behavior and the exercise of free will. In fact, Aquinas only completely excludes human unconsciousness. But there are other important properties that are not excluded from human action that figure prominently in Mises's magnum opus . For example, error is not excluded. Human courses of action may simply be mistaken, misguided, or simply unfruitful.