1. Dogmatism had been critically annihilated by Kant; his Critick of pure Reason had for its result the theoretical indemonstrableness of the three ideas of the reason, God, freedom, and immortality. True, these ideas which, from the standpoint of theoretical knowledge, had been thrust out, Kant had introduced again as postulates of the practical reason; but as postulates, as only practical premises, they possess no theoretic certainty, and remain exposed to doubt. In order to do away with this uncertainty, and this despairing of knowledge which had seemed to be the end of the Kantian philosophy, _Jacobi_, a younger cotemporary of Kant, placed himself upon the standpoint of the faith philosophy in opposition to the standpoint of criticism. Though these highest ideas of the reason, the eternal and the divine, cannot be reached and proved by means of demonstration, yet is it the very essence of the divine that it is indemonstrable and unattainable for the understanding. In order to be certain of the highest, of that which lies beyond the understanding, there is only one organ, viz., feeling. In feeling, therefore, in immediate knowledge, in faith, Jacobi thought he had found that certainty which Kant had sought in vain on the basis of discursive thinking. 2. While Jacobi stood in an antithetic relation to the Kantian philosophy, _Fichte_ appears as its immediate consequence. Fichte carried out to its consequence the Kantian dualism, according to which the Ego, as theoretic, is subjected to the external world, while as practical, it is its master, or, in other words, according to which the Ego stands related to the objective world, now receptively and again spontaneously. He allowed the reason to be exclusively practical, as will alone, and spontaneity alone, and apprehended its theoretical and receptive relation to the objective world as only a circumscribed activity, as a limitation prescribed to itself by the reason. But for the reason, so far as it is practical, there is nothing objective except as it is produced. The will knows no being but only an ought. Hence the objective being of truth is universally denied, and the thing which is essentially unknown must fall away of itself as an empty shadow. “Every thing which is, is the Ego,” is the principle of the Fichtian system, and represents at the same time the subjective idealism in its consequence and completion.