Proof.- Men, in so far as they live in obedience to reason, are most useful to their fellow men (IV:xxxv;Coroll.i.); therefore (IV:xix.), we shall in obedience to reason necessarily endeavour to bring about that men should live in obedience to reason. But the good which every man, in so far as he is guided by reason, or, in other words, follows after virtue, desires for himself, is to understand (IV:xxvi.); wherefore the good, which each follower of virtue seeks for himself, he will desire also for others. Again, desire, in so far as it is referred to the mind, is the very essence of the mind (Def. of the Emotions, i.); now the essence of the mind consists in knowledge (III:xi.), which involves the knowledge of God (II:xlvii.), and without it (I:xv.), can neither be, nor be conceived; therefore, in proportion as the mind's essence involves a greater knowledge of God, so also will be greater the desire of the follower of virtue, that other men should possess that which he seeks as good for himself. Q.E.D. Another Proof.- 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.