We stand now upon the threshold of the _Theory of Science_. It is divided into three parts. (1) General principles of a theory of science. (2) Principles of theoretical knowledge. (3) Principles of practical science.
As has already been said, there are three _supreme_ fundamental principles, one absolutely unconditioned, and two relatively unconditioned.
(1.) _The absolutely first and absolutely unconditioned fundamental principle_ ought to express that act of the mind which lies at the basis of all consciousness, and alone makes consciousness possible. Such is the principle of identity, A = A. This principle remains, and cannot be thought away, though every empirical determination be removed. It is a fact of consciousness, and must, therefore, be universally admitted: but at the same time it is by no means conditioned, like every other empirical fact, but unconditioned, because it is a free act. By affirming that this principle is certain without any farther ground, we ascribe to ourselves the faculty of _positing_ something absolutely. We do not, therefore, affirm that A is, but only that if A is, then it is equal to A. It is no matter now about the content of the principle, we need only regard its form. The principle A = A is, therefore, conditioned (hypothetically) as to its content, and unconditioned only as to its form and its connection. If we would now have a principle unconditioned in its content as well as in its connection, we put Ego in the place of A, as we are fully entitled to do, since the connection of subject and predicate contained in the judgment A = A is posited in the Ego and through the Ego. Hence A = A becomes transformed into Ego = Ego. This principle is unconditioned not only as to its connection, but also as to its content. While we could not, instead of A = A, say that A is, yet we can instead of Ego = Ego, say that Ego is. All the facts of the empirical consciousness find their ground of explanation in this, viz., that before any thing else is posited in the Ego, the Ego itself is there. This fact, that the Ego is absolutely posited and grounded on itself, is the basis of all acting in the human mind, and shows the pure character of activity in itself. The Ego _is_, because it posits itself, and it only is, because this simple positing of itself is wholly by itself. The being of the Ego is thus seen in the positing of the Ego, and on the other hand, the Ego is enabled _to posit_ simply by virtue of its being. It is at the same time the acting, and the product of the action. I am, is the expression of the only possible deed. Logically considered we have, in the first principle of a Theory of Science, A = A, the logical law of identity. From the proposition A = A, we arrive at the proposition Ego = Ego. The latter proposition, however, does not derive its validity from the former, but contrarywise. The prius of all judgments is the Ego, which posits the connection of subject and predicate. The logical law of identity arises, therefore, from Ego = Ego. Metaphysically considered, we have in this same first principle of a Theory of Science, the category of _reality_. We obtain this category by abstracting every thing from the content, and reflecting simply upon the mode of acting of the human mind. From the Ego, as the absolute subject, every category is derived.