The one fundamental prejudice to which all others are reducible, is this: that there are things outside of us; an opinion which, while it rests neither on proofs nor on conclusions (for there is not a single irrefragable proof of it), and yet cannot be uprooted by any opposite proof (_naturam furcâ expellas, tamen usque redibit_), lays claim to immediate certainty; whereas, inasmuch as it refers to something quite different from us—yea, opposed to us—and of which there is no evidence how it can come into immediate consciousness, it must be regarded as nothing more than a prejudice—a natural and original one, to be sure, but nevertheless a prejudice. The contradiction lying in the fact that a conclusion which in its nature cannot be immediately certain, is, nevertheless, blindly and without grounds, accepted as such, cannot be solved by transcendental philosophy, except on the assumption that this conclusion is implicitly, and in a manner hitherto not manifest, not founded upon, but identical, and one and the same with an affirmation which is immediately certain; and to demonstrate this identity will really be the task of transcendental philosophy. 2. Now, even for the ordinary use of reason, there is nothing immediately certain except the affirmation _I am_, which, as it loses all meaning outside of immediate consciousness, is the most individual of all truths, and the absolute prejudice, which must be assumed if anything else is to be made certain. The affirmation _There are things outside of us_, will therefore be certain for the transcendental philosopher, only through its identity with the affirmation _I am_, and its certainty will be only equal to the certainty of the affirmation from which it derives it. According to this view, transcendental knowledge would be distinguished from ordinary knowledge in two particulars. _First_—That for it the certainty of the existence of external objects is a mere prejudice, which it oversteps, in order to find the grounds of it. (It can never be the business of the transcendental philosopher to prove the existence of things in themselves, but only to show that it is a natural and necessary prejudice to assume external objects as real.) _Second_—That the two affirmations, _I am_ and _There are things outside of me_, which in the ordinary consciousness run together, are, in the former, separated and the one placed before the other, with a view to demonstrate as a fact their identity, and that immediate connection which in the other is only felt. By the act of this separation, when it is complete, the philosopher transports himself to the transcendental point of view, which is by no means a natural, but an artificial one.