3p40c2d.md (399B)
1 He who conceives, that another hates him, will (by the 2 last proposition) hate his enemy in return, and (III. xxvi.) will 3 endeavour to recall everything which can affect him painfully; 4 he will moreover endeavour to do him an injury (III. xxxix.). 5 Now the first thing of this sort which he conceives is the injury 6 done to himself; he will, therefore, forthwith endeavour to 7 repay it in kind. Q.E.D. 8 9