Thomas Aquinas

“ It is not accidental to the thing desired to be apprehended by the sense or the intellect; on the contrary, this belongs to it by its nature; for the appetible does not move the appetite except as it is apprehended. Wherefore differences in the thing apprehended are of themselves differences of the appetible. And so the appetitive powers are distinct according to the distinction of the things apprehended, as their proper objects.
Reply to Objection 2: The intellectual appetite, though it tends to individual things which exist outside the soul, yet tends to them as standing under the universal ”

“ But each power of the soul desires some particular desirable thing---namely its own suitable object. Therefore, with regard to this object which is the desirable in general, we should not assign some particular power distinct from the others, called the appetitive power. ”

“ What is apprehended and what is desired are the same in reality, but differ in aspect: for a thing is apprehended as something sensible or intelligible, whereas it is desired as suitable or good. Now, it is diversity of aspect in the objects, and not material diversity, which demands a diversity of powers. ”

“ Wherefore the Philosopher says (Rhetoric. ii, 4) that hatred can regard a universal, as when "we hate every kind of thief." In the same way by the intellectual appetite we may desire the immaterial good, which is not apprehended by sense, such as knowledge, virtue, and suchlike. ”