Jakob Friedrich Fries, a German philosopher, born at Barby, near Magdeburg, Aug. 23, 1773, died in Jena, Aug. 10, 1843. He was educated in a Moravian school, and studied philosophy at Leipsic and Jena. He passed several years in Switzerland as a private teacher, and became professor of philosophy successively at Heidelberg and Jena. Being deprived of his professorship for having taken part in the democratic movement of 1819, he was in 1824 appointed to the chair of physics and mathematics in the latter university, which he held till his death. His works include Neue oder anthropologische Kritik der Vernunft (2d ed., 3 vols., 182S-'31), and many other writings, chiefly upon problems of speculative philosophy. Proceeding from Kant, he inclines to the doctrine of faith as developed in the system of Jacobi. He maintains that there is only subjective certainty, that mental phenomena are the only objects of knowledge, but recognizes a principle which he names faith, by which we have a presentiment of the existence of outward things, and of the eternal existence of the ideas of the pure reason.-See Jakob Friedrich Fries, by E. L. T. Henke (Leipsic, 1867).