But the problem demands only the explanation of that agreement generally, and leaves it entirely undecided where the explanation shall begin, what it shall make its first, and what its second. Moreover, as the two opposites are mutually necessary to each other, the result of the operation must be the same, from whichever point it sets out. To make the objective the first, and derive the subjective from it, is, as has just been shown, the task of natural philosophy. If, therefore, there is a transcendental philosophy, the only course that remains for it is the opposite one, namely: to set out from the subjective as the first and the absolute, and deduce the origin of the objective from it. Into these two possible directions of philosophy, therefore, natural and transcendental philosophy have separated themselves; and if all philosophy must have for its aim to make either an Intelligence out of Nature or a Nature out of Intelligence, then transcendental philosophy, to which the latter task belongs, is the other necessary fundamental science of philosophy. II.—COROLLARIES. In the foregoing we have not only deduced the idea of transcendental philosophy, but have also afforded the reader a glance into the whole system of philosophy, composed, as has been shown, of two principal sciences, which, though opposed in principle and direction, are counter-parts and complements of each other. Not the whole system of philosophy, but only one of the principal sciences of it, is to be here discussed, and, in the first place, to be more clearly characterized in accordance with the idea already deduced. 1. If, for transcendental philosophy, the subjective is the starting point, the only ground of all reality, and the sole principle of explanation for everything else, it necessarily begins with universal doubt regarding the reality of the objective. As the natural philosopher, wholly intent upon the objective, seeks, above all things, to exclude every admixture of the subjective from his knowledge, so, on the other hand, the transcendental philosopher seeks nothing so much as the entire exclusion of the objective from the purely subjective principle of knowledge. The instrument of separation is absolute scepticism—not that half-scepticism which is directed merely against the vulgar prejudices of mankind and never sees the foundation—but a thorough-going scepticism, which aims not at individual prejudices, but at the fundamental prejudice, with which all others must stand or fall. For over and above the artificial and conventional prejudices of man, there are others of far deeper origin, which have been placed in him, not by art or education, but by Nature itself, and which pass with all other men, except the philosopher, as the principles of knowledge, and with the mere self-thinker as the test of all truth.