Its significance may be further developed by comparing it with the scientific postulate. All science rests upon the conviction of the thorough-going and permanent unity of the world of objects known--a unity which is sometimes termed the 'uniformity of nature' or the 'reign of law'; without this conviction that objects are not mere isolated and transitory appearances, but are connected together in a system by laws or relations, science would be an impossibility. Moral experience _makes for the world of practice_ an assumption analogous in kind to that which intellectual experience makes for the world of knowledge. And just as it is not the affair of science, as such, or even of logic (the theory of science) to justify this presupposition of science, or to do more than show its presence in intellectual experience, so it is not the business of conduct, or even of ethics (the theory of conduct) to justify what we have termed the 'ethical postulate'. In each case the further inquiry belongs to metaphysics. XLI. Does the End Proposed Serve as a Criterion of Conduct? We have now concluded that an end which may be termed indifferently 'The Realization of Individuality', 'The Performance of Specific Functions', 'The Satisfaction of Interests', 'The Realization of a Community of Individuals' is the moral end. Will this end serve the two aims (see Sec. XVI) required of a criterion, or standard: (1) Will it unify individual conduct? (2) Will it afford a common good? We have just been endeavoring to show that it does both of these things; that as the realization of one's specific capacity, it unifies individual conduct, and that, as the performance of function, it serves to satisfy the entire community. To take up just these points, accordingly, would involve a repetition of what has been said, and we shall therefore take up instead some aspects of the individual and social unity of conduct, not already considered.