The act of a cognitive power is commanded by the appetitive power, which moves all the powers, as stated above (I-II:09:1). Wherefore knowledge regards a twofold good. One is connected with the act of knowledge itself; and this good pertains to the intellectual virtues, and consists in man having a true estimate about each thing. The other good pertains to the act of the appetitive power, and consists in man's appetite being directed aright in applying the cognitive power in this or that way to this or that thing. And this belongs to the virtue of studiousness. Wherefore it is reckoned among the moral virtues.
[Thomas Aquinas, ST 2-2.166.2 ad 2.]
