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II.
§ 17. In the first book we considered the idea merely as such, that is, only according to its general form. It is true that as far as the abstract idea, the concept, is concerned, we obtained a knowledge of it in respect of its content also, because it has content and meaning only in relation to the idea of perception, without which it would be worthless and empty. Accordingly, directing our attention exclusively to the idea of perception, we shall now endeavour to arrive at a knowledge of its content, its more exact definition, and the forms which it presents to us. And it will specially interest us to find an explanation of its peculiar significance, that significance which is otherwise merely felt, but on account of which it is that these pictures do not pass by us entirely strange and meaningless, as they must otherwise do, but speak to us directly, are understood, and obtain an interest which concerns our whole nature.
We direct our attention to mathematics, natural science, and philosophy, for each of these holds out the hope that it will afford us a part of the explanation we desire. Now, taking philosophy first, we find that it is like a monster with many heads, each of which speaks a different language. They are not, indeed, all at variance on the point we are here considering, the significance of the idea of perception. For, with the exception of the Sceptics and the Idealists, the others, for the most part, speak very much in the same way of an object which constitutes the basis of the idea, and which is indeed different in its whole being and nature from the idea, but yet is in all
