Renouvier has shown the origin of the notion of Justice as arising primarily from an association of two persons. “Reason established a kind of community and moral solidarity in this reciprocity.”[18] This right and duty unite to constitute Justice. It is truly said that it is just to fulfil one’s duty, just to demand one’s right, and Justice is formed by a union of these two in such a manner that they always complement one another. Bearing in mind the doctrine of personality as an end, we get a general law of action which may be stated in these terms: “Always act in such a way that the maxim applicable to your act can be erected by your conscience into a law common to you and your associate.” Now to apply this to an association of any number of persons—_e g._, human society as a whole—we need only generalise it and state it in these terms: “Act always in such a way that the maxim of your conduct can be erected by your conscience into a universal law or formulated in an article of legislation which you can look upon as expressing the will of every rational being.” This “categorical obligation” is the basis of ethics. It stands clear of hypothetical cases as a general law of action, and “there is no such thing really as practical morality,” remarks Renouvier, “except by voluntary obedience to a law.”[19] [18] _Ibid_., pp. 79-80. [19] _Science de la Morale_, vol. I, p. 100. The fulfilment of our duties to ourselves generally tends to fit us for fulfilling our duties to others, and the neglect of the former will lead inevitably to inability to perform these latter. Our duty to others thus involves our duty to ourselves.[20] [20] The notion of self-sacrifice itself involves also, to a degree, the maintenance of self, without which there could be no self to sacrifice. History has frequently given examples of men of all types refusing to sacrifice their lives for a certain cause because they wished to preserve them for some other (and possibly better—in their minds at any rate, better) form of self-sacrifice.