This love of a partner cannot proceed from the relation or connexion betwixt us, in the same manner as I love a brother or countryman. A rival has almost as close a relation to me as a partner. For, as the pleasure of the latter causes my pleasure, and his pain my pain; so the pleasure of the former causes my pain, and his pain my pleasure. The connexion, then, of cause and effect, is the same in both cases; and if, in the one case, the cause and effect has a farther relation of resemblance, they have that of contrariety in the other; which, being also a species of resemblance, leaves the matter pretty equal. The only explication, then, we can give of this phenomenon, is derived from that principle of a parallel direction above-mentioned. Our concern for our own interest gives us a pleasure in the pleasure, and a pain in the pain of a partner, after the same manner as by sympathy we feel a sensation correspondent to those which appear in any person who is present with us. On the other hand, the same concern for our interest makes us feel a pain in the pleasure, and a pleasure in the pain of a rival; and, in short, the same contrariety of sentiments as arises from comparison and malice. Since, therefore, a parallel direction of the affections, proceeding from interest, can give rise to benevolence or anger, no wonder the same parallel direction, derived from sympathy and from comparison, should have the same effect. In general we may observe, that 'tis impossible to do good to others, from whatever motive, without feeling some touches of kindness and good will towards them; as the injuries we do not only cause hatred in the person who suffers them, but even in ourselves. These phenomena, indeed, may in part be accounted for from other principles.