But there is quite another type of uniformity which we are ever discovering and appealing to, if not in the whole of nature, at least in many of its parts. Hume calls it “unity of plan,” and he points to the general adaptation of the organs of the body to the end of preserving the life of that body. And where we find such adaptation of various means to a single end, we ascribe life and even intelligence to the organic whole. Nature, from this point of view, is full of life and intelligence. Or, rather, should we not say it is full of _lives and intelligences_? Here indeed, is the difficulty; can we treat the whole cosmos as one great organism? Can we find one supreme end that all the obvious minor ends subserve, as they in turn are served by diverse means? Or, as another similar possibility, can we establish an analogy between the cosmos and a machine of human invention, an implement of the arts,--a watch, say, to follow Paley’s argument? Here, too, we must find a purpose, for a machine is not merely a mechanism--it is a mechanism with a function. Many excellent minds have expended themselves on this problem, whose difficulty is supreme, and I think we shall not be far wrong in asserting that it is at moments when the issue presents itself in this way to Hume’s mind that “doubt,” as he says, “uncertainty, suspense of judgment appear the only result of our most accurate scrutiny.” There seems something beyond Hume’s usual imperturbability in the words with which one of his dialogues concludes: “Believe me, Cleanthes, the most natural sentiment which a well-disposed mind will feel on this occasion, is a longing desire and expectation that Heaven would be pleased to dissipate, at least alleviate, this profound ignorance, by affording some more particular revelation to mankind, and making discoveries of the nature, attributes and operations of the divine object of our faith.”[3] But perhaps this is only a phrase, for nowhere else do the lips of Hume shape the words “revelation” and “faith” but that the lines of mockery are seen to form around them. * * * * * In this state of mind respecting theology, it is inevitable that Hume should struggle in quite a pagan spirit with the problem of human wisdom. Our experience of life being what it is, how may man most successfully attain to happiness, and what relation has the line of conduct which prudence would recommend to that which has been traditionally regarded as virtuous? But first, _has_ there been any one principle of conduct that defines it as virtuous; or are there as many notions of virtue as there are communities with more or less independent traditions? It is a problem of ethics upon which every inquirer from Socrates down has spent his best thought.