In one sense, the knowledge of Nature is subjective, for it depends on our mental constitution, and on the laws of our knowing faculty. But religious and moral knowledge is subjective in a different manner and for a deeper reason. The object of scientific knowledge is always outside the ego, and it is in knowing it as an object outside the ego that the objectivity of that knowledge consists. But the object of religious or moral knowledge--God, the Good, the Beautiful--these are not phenomena that may be grasped outside the ego and independently of it. God only reveals Himself in and by piety; the Good, in the consciousness of the good man; the Beautiful, in the creative activity of the artist. This is only saying that the object of these kinds of knowledge is immanent in the subject himself, and only reveals itself by the personal activity of that subject. Absolutely eliminate the religious and moral subject, or rather take from him all personal activity, and you suppress, for him, the object of morality and religion. Let us take up again that striking antithesis of the two orders of knowledge. What is at once the basis and the sign of the objectivity of the natural sciences? One may theoretically ask whether the world of science, the world that _appears_ to us, is exactly the real world, existing outside of us. It is thus that in the philosophy of Kant the famous question as to _the thing in itself_ is stated. But it is equally certain that in the name of that philosophy this question ought logically to be discarded. One is astonished that the author of the _Critique of Pure Reason_ did not immediately close that door opened to scientific scepticism. After his critique, in fact, it is evident that that substratum which some are forced to imagine as a support to phenomena--that the indeterminate and indeterminable substance that they represent beneath the forms and qualities of things,--is both a non-being and nonsense. _Das Ding an sich ist ein Unding_. (The thing in itself is an unthing.) It is a remnant of ancient metaphysics which ought to be eliminated from modern philosophy. In allowing it to introduce itself into our theory of knowledge, it overturns it as would a heterogeneous element. He that persists in distinguishing between the thing in itself and the phenomenal thing will never be able to give an account of the objectivity of the sciences of Nature, and of the kind of certitude that belongs to them. That which appears to us from without is not doubtless all the reality of the world; but it is a real world. By his calculations, Leverrier came first to suspect the existence of a large planet as yet unperceived; then he came to measure its volume, to trace its orbit, and finally to mark its place at a given time. He said to his brother astronomers: "Look there!" and the planet appeared at the end of their telescopes.