Compassion is the Ultimate Justice
Compassion is a natural feeling, which, by moderating the violence of love of self in each individual, contributes to the preservation of the whole species. It is this compassion that hurries us without reflection to the relief of those who are in distress: it is this which in a state of nature supplies the place of laws, morals and virtues, with the advantage that none are tempted to disobey its gentle voice: it is this which will always prevent a sturdy savage from robbing a weak child or a feeble old man of the sustenance they may have with pain and difficulty acquired, if he sees a possibility of providing for himself by other means: it is this which, instead of inculcating that sublime maxim of rational justice. Do to others as you would have them do unto you, inspires all men with that other maxim of natural goodness, much less perfect indeed, but perhaps more useful; Do good to yourself with as little evil as possible to others. In a word, it is rather in this natural feeling than in any subtle arguments that we must look for the cause of that repugnance, which every man would experience in doing evil, even independently of the maxims of education.
Jean-Jacques Rousseau, in 'Discourse on the Origin of Inequality'