[P31: If we imagine that someone loves, desires or hates something we ourselves love, desire, or hate, we shall thereby love, desire or hate it with greater constancy. But if we imagine that he is averse to what we love, or the opposite {NS: that he loves what we hate}, then we shall undergo vacillation of mind.

Dem.: Simply because we imagine that someone loves something, we thereby love the same thing (by P27). But we suppose that we already love it without this {cause of love}; so there is added to the Love a new cause, by which it is further encouraged. As a result, we shall love what we love with greater constancy.

Next, from the fact that we imagine someone to be averse to something, we shall be averse to it (by P27). But if we suppose that at the same time we love it, then at the same time we shall both love and be averse to the same thing, or (see P17 S) we shall undergo vacillation of mind, q.e.d.

Cor.: From this and from P28 it follows that each of us strives, so far as he can, that everyone should love what he loves, and hate what he hates. Hence that passage of the poet: Speremus pariter, pariter metuamus amantes; Ferreus est, si quis, quod sink alter, amat.

Translation

Let us hope together, let us fear together, lovers; It is hard if one loves what another hates.

Schol.: This striving to bring it about that everyone should approve his love and hate is really Ambition (see P29 S). And so we see that each of us, by his nature, wants the others to live according to his temperament; when all alike want this, they are alike an obstacle to one another, and when all wish to be praised, or loved, by all, they hate one another.