4p34d.md (806B)
1 A man, for instance Peter, can be the cause of Paul's 2 feeling pain, because he (Peter) possesses something similar to 3 that which Paul hates (III. xvi.), or because Peter has sole 4 possession of a thing which Paul also loves (III. xxxii. and 5 note), or for other causes (of which the chief are enumerated in 6 III. lv. note); it may therefore happen that Paul should hate 7 Peter (Def. of Emotions, vii.), consequently it may easily happen 8 also, that Peter should hate Paul in return, and that each should 9 endeavour to do the other an injury, (III. xxxix.), that is (IV. 10 xxx.), that they should be contrary one to another. But the 11 emotion of pain is always a passion or passive state (III. lix.); 12 hence men, in so far as they are assailed by emotions which are 13 passions, can be contrary one to another. Q.E.D. 14 15