For materialism was the most consistent system starting from the object, as this is the most consistent system starting from the subject. Materialism overlooked the fact that, with the simplest object, it assumed the subject also; and Fichte overlooked the fact that with the subject (whatever he may call it) he assumed the object also, for no subject is thinkable without an object. Besides this he forgot that all _a priori_ deduction, indeed all demonstration in general, must rest upon some necessity, and that all necessity is based on the principle of sufficient reason, because to be necessary, and to follow from given grounds are convertible conceptions.(10) But the principle of sufficient reason is just the universal form of the object as such. Thus it is in the object, but is not valid before and outside of it; it first produces the object and makes it appear in conformity with its regulative principle. We see then that the system which starts from the subject contains the same fallacy as the system, explained above, which starts from the object; it begins by assuming what it proposes to deduce, the necessary correlative of its starting-point. The method of our own system is _toto genere_ distinct from these two opposite misconceptions, for we start neither from the object nor from the subject, but from the _idea_, as the first fact of consciousness. Its first essential, fundamental form is the antithesis of subject and object. The form of the object again is the principle of sufficient reason in its various forms. Each of these reigns so absolutely in its own class of ideas that, as we have seen, when the special form of the principle of sufficient reason which governs any class of ideas is known, the nature of the whole class is known also: for the whole class, as idea, is no more than this form of the principle of sufficient reason itself; so that time itself is nothing but the principle of existence in it, _i.e._, succession; space is nothing but the principle of existence in it, _i.e._, position; matter is nothing but causality; the concept (as will appear immediately) is nothing but relation to a ground of knowledge. This thorough and consistent relativity of the world as idea, both according to its universal form (subject and object), and according to the form which is subordinate to this (the principle of sufficient reason) warns us, as we said before, to seek the inner nature of the world in an aspect of it which is _quite different and quite distinct from the idea_; and in the next book we shall find this in a fact which is just as immediate to every living being as the idea. But we must first consider that class of ideas which belongs to man alone. The matter of these is the concept, and the subjective correlative is reason, just as the subjective correlative of the ideas we have already considered was understanding and sensibility, which are also to be attributed to all the lower animals.(11)