for raising new issues.
PROP. XL. Whatsoever conduces to man's social life, or causes men to live together in harmony, is useful, whereas whatsoever brings discord into a State is bad.
Proof.—For whatsoever causes men to live together in harmony also causes them to live according to reason (IV. xxxv.), and is therefore (IV. xxvi. xxvii.) good, and (for the same reason) whatsoever brings about discord is bad. Q.E.D.
PROP. XLI. Pleasure in itself is not bad but good: contrariwise, pain in itself is bad.
Proof.—Pleasure (III. xi. and note) is emotion, whereby the body's power of activity is increased or helped; pain is emotion, whereby the body's power of activity is diminished or checked; therefore (IV. xxxviii.) pleasure in itself is good, &c. Q.E.D.
PROP. XLII. Mirth cannot be excessive, but is always good; contrariwise, Melancholy is always bad.
Proof.—Mirth (see its Def. in III. xi. note) is pleasure, which, in so far as it is referred to the body, consists in all parts of the body being affected equally: that is