Kant, however, in the Critique of Judgement is sadly fettered by the chains that he himself had forged, and frequently chafes under the restraints they impose. He indicates more than once a point of view higher than that of the Critique of Pure Reason, from which the phenomena of life and mind may be contemplated. He had already hinted in that work that the supersensible substrate of the ego and the non-ego might be identical. “Both kinds of objects differ from each other, not internally, but only so far as the one _appears_ external to the other; possibly what is at the basis of phenomenal matter as a thing in itself may not be so heterogeneous after all as we imagine.”[4] This hypothesis which remains a bare undeveloped possibility in the earlier work is put forward as a positive doctrine in the Critique of Judgement. “There must,” says Kant, “be a ground of the _unity_ of the supersensible, which lies at the basis of nature, with that which the concept of freedom practically contains” (Introduction, p. 13). That is to say, he maintains that to explain the phenomena of organic life and the purposiveness of nature we must hold that the world of sense is not disparate from and opposed to the world of thought, but that _nature is the development of freedom_. The connexion of nature and freedom is suggested by, nay is involved in, the notion of natural adaptation; and although we can arrive at no knowledge of the supersensible substrate of both, yet such a common ground there must be. This principle is the starting-point of the systems which followed that of Kant; and the philosophy of later Idealism is little more than a development of the principle in its consequences.