E4P37D2
Demonstration 2 of Proposition 37 — Part IV
Latin
Bonum quod homo sibi appetit et amat, constantius amabit si viderit alios idem amare (per propositionem 31 partis III) atque adeo (per corollarium ejusdem propositionis) conabitur ut reliqui idem ament et quia hoc bonum (per propositionem præcedentem) omnibus commune est eoque omnes gaudere possunt, conabitur ergo (per eandem rationem) ut omnes eodem gaudeant et (per propositionem 37 partis III) eo magis quo hoc bono magis fruetur. Q.E.D.
English (Elwes 1883)
The good, which a man desires for himself and loves, he will love more constantly, if he sees that others love it also (III. xxxi.); he will therefore endeavour that others should love it also; and as the good in question is common to all, and therefore all can rejoice therein, he will endeavour, for the same reason, to bring about that all should rejoice therein, and this he will do the more (III. xxxvii.), in proportion as his own enjoyment of the good is greater.
Modern English
A good that a person seeks and loves for himself, he will love more steadily if he sees that others love it as well (E3P31). He will therefore strive to bring it about that others love it too. And since this good (E4P36) is common to all and all can rejoice in it, he will strive for the same reason to bring it about that all rejoice in it — and the more so (E3P37) in proportion as his own enjoyment of this good is greater. Q.E.D.