Moses Mendelssohn, a German philosopher, born in Dessau, Sept. 6,1729, died Jan. 4,1786. His father was a Jewish transcriber of the Pentateuch and master of a Hebrew day school. He was early sent to the public Talmud school, where he was taught the Mishnah and Gemara, and at the age of seven was usually called up at 3 or 4 o'clock in the morning to proceed to the severe tasks of the school. Even at that age he manifested a spirit of thorough inquiry, and mastered the Hebrew language, so that he could write it with purity and elegance. He subsequently conceived an enthusiastic love for the " Guide of the Perplexed" (Moreh nebukhim) of Maimonides, and his severe study of it laid the foundation at once of his mental culture and of a chronic nervous disease. About 1745 he followed his friend and teacher Rabbi Frankel to Berlin, and he lived there several years in extreme poverty. He became intimate with the mathematician Israel Moses, under whom he studied Euclid in a Hebrew translation, and with whom he discussed what he read in Latin and German. Through other friends he obtained elementary instruction in the French and English languages.

It had been his custom whenever he purchased a loaf to notch it according to his pecuniary prospects into so many meals, never eating according to his appetite, but to his finances. In 1750 he became acquainted with an opulent Jewish manufacturer named Bern-hard, and was admitted into his family at first as tutor to his children. In 1754 he became his bookkeeper. He now made the acquaintance of Lessing, and the latter pages of the Morgen-stunden record their enduring mutual affection. Their recognized intimacy, and the accession of Nicolai and Abbt to the circle, contributed much to overthrow the Judaiophobia then so prevalent in Germany. In 1755 he published a treatise Ueber die Empfindungen, a profound disquisition on problems of aesthetics.

This was followed by other short treatises, which were collected under the title of Philo-sophische Sehriften (Berlin, 1701). He was one of the most active contributors to the Bi-bliothek der schonen Wissenschaften, and to the Briefe, die neueste Literatur betreffend. In 1763 the royal academy of Berlin awarded him the prize for a memoir on the question: " Are metaphysics susceptible of mathematical demonstration?" though Kant was one of his competitors. The death of his first child in the same year was the occasion of his defending Spalding against Abbt in their controversy on human destiny; and subsequently, imitating Plato's " Phasdo," and adding all the arguments for the immortality of the soul suggested by the philosophy of later periods, he produced his Phaedon, oder uber die Unsterblichheit der Seele (Berlin, 1767), which was soon translated into almost all European languages, as well as into Hebrew. Mendelssohn's fame was at its height when he received a public challenge from La-vater either to refute Bonnet's arguments in support of Christianity or to renounce Judaism. He answered the challenge with an adroitness and candor that drew from Lavater an apology and retraction of his peremptory address. The agitation caused by this matter induced a long and dangerous illness.

Mendelssohn exerted an immense influence by his efforts for the elevation of his coreligionists. His German translation of the Pentateuch and metrical version of the Psalms are admirable for elegance and perspicuity; and their publication, accompanied by Scriptural comments in Hebrew by himself and a circle of friends, marks an epoch in the history of modern Judaism. In defence of the rights of his Jewish brethren he wrote the introduction to his translation of Rabbi Menasseh ben Israel's "Defence of the Jews" (Berlin, 1782). In 1783 appeared his Jerusalem, oder uber religiose Macht und Judenthum, a vindication both of religious tolerance and of Judaism, and still one of the best books on those topics. He published in 1785 Morgenstunden, consisting of lectures on the existence of God. It contains an affectionate memorial of Lessing, and was the occasion of Jacobi's letters to him Ueber die Lelire des Spinoza, in which Lessing was charged with being a Spinozist. Mendelssohn immediately answered in a dissertation addressed An die Freunde Lessings. His health was seriously injured by the excitement attending this effort, and a slight cold terminated fatally.

The most complete edition of his works appeared under the care of his grandson G. B. Mendelssohn (7 vols., Lcipsic, 1843-'5). His life has been written, among others, by Samuels (2d ed., London, 1822) and Kay-serling (Berlin, 1862).