4p8d.md (844B)
1 We call a thing good or evil, when it is of service or 2 the reverse in preserving our being (IV. Deff. i. and ii.), that 3 is (III. vii.), when it increases or diminishes, helps or 4 hinders, our power of activity. Thus, in so far as we perceive 5 that a thing affects us with pleasure or pain, we call it good or 6 evil; wherefore the knowledge of good and evil is nothing else 7 but the idea of the pleasure or pain, which necessarily follows 8 from that pleasurable or painful emotion (II. xxii.). But this 9 idea is united to the emotion in the same way as mind is united 10 to body (II. xxi.); that is, there is no real distinction 11 between this idea and the emotion or idea of the modification of 12 the body, save in conception only. Therefore the knowledge of 13 good and evil is nothing else but the emotion, in so far as we 14 are conscious thereof. Q.E.D. 15 16