=Hitherto it has been supposed that all knowledge must conform to the objects.=[123]--This statement is historically correct. That assumption did actually underlie one and all of the pre-Kantian philosophies. At the same time, it is true that Kant’s phenomenalist standpoint is partially anticipated by Hume, by Malebranche and by Leibniz, especially by the first named. Hume argues that to condemn knowledge on the ground that it can never copy or truly reveal any external reality is to misunderstand its true function. Our sense perceptions and our general principles are so determined by nature as to render feasible only a practical organisation of life. When we attempt to derive from them a consistent body of knowledge, failure is the inevitable result.[124] Malebranche, while retaining the absolutist view of conceptual knowledge, propounds a similar theory of sense-perception.[125] Our perceptions are, as he shows, permeated through and through, from end to end, with illusion. Such illusions justify themselves by their practical usefulness, but they likewise prove that theoretical insight is not the purpose of our sense-experience. Kant’s Copernican hypothesis consists in great part of an extension of this view to our conceptual, scientific knowledge. But he differs both from Malebranche and from Hume in that he develops his phenomenalism on rationalist lines. He professes to show that though our knowledge is only of the phenomenal, it is conditioned by _a priori_ principles. The resulting view of the distinction between appearance and reality has kinship with that of Leibniz.[126] The phenomena of science, though only appearances, are none the less _bene fundata_. Our scientific knowledge, though not equivalent to metaphysical apprehension of the ultimately real, can be progressively developed by scientific methods. =The two “parts” of metaphysics.=[127]--Kant is here drawing the important distinction, which is one result of his new standpoint, between _immanent_ and _transcendent_ metaphysics. It is unfortunate that he does not do so in a more explicit manner, with full recognition of its novelty and of its far-reaching significance. Many ambiguities in his exposition here and elsewhere would then have been obviated.[128] =The unconditioned which Reason postulates in all things by themselves, by necessity and by right.=[129]--Points are here raised the discussion of which must be deferred. Cf. below, pp. 429-31, 433-4, 558-61. =The Critique is a treatise on method, not a system of the science itself.=[130]--Cf. A xv.; B xxxvi.; and especially A 11 = B 24, below pp. 71-2.