The duty of returning good for evil goes even further than clemency and the pardon of injuries: for this is nothing more than to abstain from wronging one's enemies. But we should do more: we must be capable of doing good to our enemies when they deserve it, or need it; and further still, we should try to carry the virtue even so far as to interdict ourselves any feeling of pride, which would naturally arise in a heart great enough to avenge itself by benefits. The philosopher Spinoza has admirably expressed this doctrine: "Hatred must be overcome not by hatred, but by love and generosity." =74. Duties of kindness towards animals.=--Among the moralists, there are some who do not admit that we have any duties towards beings inferior to man, namely, animals; others, on the contrary, do not admit any duties towards any above man, consequently towards God; others, in fine, deny that man has any towards himself. There are scarcely any duties, except those towards our fellow-beings, that have not been questioned by one or the other of the moralists: some connecting the latter with the duties towards ourselves, or the duties towards God. According to us, there are four classes of duties, and these four classes are not reducible the one to the other.[52] No one can deny from a practical point of view that there are duties towards animals; for we know very well that it is not permitted to maltreat them or cause them unnecessary pain; and every enlightened conscience condemns cruelty to animals. Therefore can there be here question only of a speculative scruple. It can be very well seen that there is a duty here; but it is, they say, a duty towards ourselves; for it is our duty not to be cruel, and cruelty toward animals accustoms us too easily to cruelty toward men. But this is a very useless subtlety, and too roundabout a way to express a very simple thing. We prefer simply saying that kindness toward an animal is a duty toward that animal. Besides, the reasons given against the duties toward animals, appear to us more specious than substantial. It is said that animals, having neither will nor intelligence, are not _persons_, but _things_; that, consequently, they have no _rights_, and that we can have no duties toward what has no rights.