This was the idealism which Kant taught and Fichte promoted. Of the other idealism there are no doubt abundant traces in the language of Kant: and they were greedily fastened on by Schopenhauer. To him the doctrine, that the world is my idea, is adequately represented when it is translated into the phrase that the world is a phantasmagoria of my brain; and escape from the subjective idealism thus initiated is found by him only through a supposed revelation of immediate being communicated in the experience of will. But according to the more consistently interpreted Kant, the problem of philosophy consists in laying bare the supreme law or conditions of consciousness on which depend the validity of our knowledge, our estimates of conduct, and our aesthetic standards. And these roots of reality are for Kant in the mind—or, should we rather say—in mind—in “Consciousness in General.” In the _Criticism of Pure Reason_ the general drift of his examination is to show that the great things or final realities which are popularly supposed to stand in self-subsistent being, as ultimate and all-comprehensive objects set up for knowledge, are not “things” as popularly supposed, but imperative and inevitable ideas. They are not objects to be known—(these are always finite): but rather the unification, the basis, or condition, and the completion of all knowledge. To know them—in the ordinary petty sense of knowledge—is as absurd and impossible as it would be, in the Platonic scheme of reality, to know the idea of good which is “on the further side of knowledge and being.” God and the Soul—and the same would be true of the World (though modern speculators sometimes talk as if they had it at least within their grasp)—are not mere _objects_ of knowledge. It would be truer to say they are that by which we know, and they are what in us knows: they make knowledge possible, and actual. Kant has sometimes spoken of them as the objects of a faith of reason. What he means is that reason only issues in knowledge because of and through this inevitable law of reason bidding us go on for ever in our search, because there can be nothing isolated and nowhere any _ne plus ultra_ in science, which is infinite and yet only justified as it postulates or commands unity.