4p42d.md (641B)
1 Mirth (see its Def. in III. xi. note) is pleasure, 2 which, in so far as it is referred to the body, consists in all 3 parts of the body being affected equally: that is (III. xi.), 4 the body's power of activity is increased or aided in such a 5 manner, that the several parts maintain their former proportion 6 of motion and rest; therefore Mirth is always good (IV. xxxix.), 7 and cannot be excessive. But Melancholy (see its Def. in the 8 same note to III. xi.) is pain, which, in so far as it is 9 referred to the body, consists in the absolute decrease or 10 hindrance of the body's power of activity; therefore (IV. 11 xxxviii.) it is always bad. Q.E.D. 12 13