Sadness is a man’s passage from a greater to a lesser perfection.

Exp.: I say a passage. For Joy is not perfection itself. If a man were born with the perfection to which he passes, he would possess it without an affect of Joy.

This is clearer from the affect of Sadness, which is the opposite of joy. For no one can deny that Sadness consists in a passage to a lesser perfection, not in the lesser perfection itself, since a man cannot be saddened insofar as he participates in some perfection. Nor can we say that Sadness consists in the privation of a greater perfection. For a privation is nothing, whereas the affect of Sadness is an act, which can therefore be no other act than that of passing to a lesser perfection, i.e., an act by which man’s power of acting is diminished or restrained (see P11 S).

As for the definitions of Cheerfulness, Pleasure, Melancholy, and Pain, I omit them, because they are chiefly related to the Body, and are only Species of Joy or Sadness.