Summa summae S. Thomae, Tomus II

I say 1°: The intellect moves the will as to specification; but the will moves the intellect and the other powers subject to it as to exercise.

Prob. the first part ¹ . To move as to specification is to determine to an act of a certain species. Yet the intellect, proposing the object to the will, determines it to an act of a certain species. Therefore. — Prob. min. The will elicits not an act of such species, e.g., of love, except because it tends toward the object proposed to it by the intellect as amiable. Therefore.

Prob. the second part ² . In all active powers ordered among themselves, that power which regards the universal end moves to exercise the powers which regard particular ends. And this appears both in natural things and in political. For heaven, which acts toward the universal conservation of generable things, moves all inferior things, each of which acts toward the conservation of its own species or even individual. Also the king, because he intends the common good of the whole kingdom, moves by his command the individual prefects of cities, who devote care of government to the several cities. Yet the object of the will is good and end in common; but each power is compared to some proper good suiting itself, as sight to perception of color, intellect to cognition of truth. Therefore the will, in the manner of an agent, moves to exercise all the powers of the soul toward their acts, besides the natural forces of the vegetative part, which are not subject to our arbitrium. This second part of the conclusion will be explained more specially in question 17, where commanded acts are treated of.

I say 2°: The will is not moved directly as to specification by the sensitive appetite, nor by the heavenly body, yet well indirectly and mediately ³ .

Prob. the first part ⁴ . Nothing material or corporeal, such are the sensitive appetite and the heavenly body, can naturally act directly upon an immaterial thing, such is the will. Therefore.

Prob. the second part ⁵ . Passion raised up in the sensitive appetite, man is affected in a certain way and changed into a certain disposition, whereby it happens that his intellect apprehends something as convenient and good which he would not thus have apprehended and judged with the passion absent. « For such as anyone is, such does the end seem to him, » as says the Philosopher, III Ethic., c. 4. Thus the angry man judges vengeance convenient and good for him, which pacified he would not judge such. Yet, as we said, the object apprehended through intellect moves the will as to specification. Therefore the sensitive appetite, from the fact that the object is represented under the notion of convenient to the intellect, moves the will as to specification indirectly and mediately, namely through the mediation of the judgment of the intellect.

Prob. the same second part concerning the heavenly body ⁶ . Heavenly bodies can alter human bodies, from which alteration follow passions in the sensitive appetite, which is the act of a bodily organ. Yet from the sensitive appetite the will is moved indirectly and mediately, as I just now said. Therefore.