3p40d.md (452B)
1 He who conceives another as affected with hatred, will 2 thereupon be affected himself with hatred (III. xxvii.), that is, 3 with pain, accompanied by the idea of an external cause. But, by 4 the hypothesis, he conceives no cause for this pain except him 5 who is his enemy; therefore, from conceiving that he is hated by 6 some one, he will be affected with pain, accompanied by the idea 7 of his enemy; in other words, he will hate his enemy in return. 8 Q.E.D. 9 10