LEIBOWITZ, YESHAYAHU (1903-1994), An Israeli scientist and philosopher. Leibowitz was born in Riga and learned chemistry and philosophy at the University of Berlin, where he received his doctorate in 1924. He also studied medicine and became a medical doctor in 1934 at the University of Basel. In 1935 he settled in Palestine and joined the stuff of the Hebrew University. He was appointed professor of organic and biochemistry and neurophysiology. His research was concerned with saccharides and enzymes in chemistry and with the nervous system of the heart in physiology. He was the head of the biological chemistry department at the Hebrew University and professor of neurophysiology at the HU Medical School. He also taught the history and philosophy of science. Yet Leibowitz was not only an academician. He was involves in public affairs and had a unique approach to Judaism. As such he was a popular lecturer, who loved to appear before diverse audiences, also frequently on radio and television. Leibowitz served as editor in chief of several volumes of the Encyclopedia Hebraica. His writings are found mostly in periodicals: Gilyonot, De'ot, Be-Terem, Petahim and Moznayim, and also in the newspaper Haaretz. A selection of lectures and articles from the period 1942-53 was published in book form, entitled Torah u-Mitzvot ba-Zeman ha-Ze (1954). His book of collected essays, Yahadut, Am Yehudi u-Medinat Yisrael ("Judaism, Jewish People, and the State of Israel", 1975) stated his philosophy and views. Other books (published in 1965 and 1982) testify to his broad knowledge and great interest in Jewish life. He also wrote on Maimonides, The Sayings of the Fathers, and the weekly Torah-portion. In 1992 Eliezer Goldman published a collection of Leibowitz's essays in English under the title Judaism, Human Values and the Jewish State, making him known internationally. Theocentrism and Humanism Leibowitz regarded Judaism has a religious and historical phenomenon, which is characterized by a recognition of the duty to serve God in performing Mitzvot. The service of God according to binding halakhic norms must be "for its own sake" (li-shema), and its purpose is not designed to achieve personal perfection or to improve society. Religion is thus not a means toward any specific end. Judaism is for Leibowitz not humanism, or a sentiment or a bundle of memories. Jews have the obligation to take upon themselves the yoke of Torah and Mitzvot. Leibowitz's standpoint is thus neither anthropocentric or ethnocentric, but theocentric. Consistent with is own reasoning, Leibowitz refused to be called a "humanist," because this is an anthropocentric notion that envisages the human being as a supreme value. Under the influence of Maimonides, Leibowitz stressed the transcendence of God, whom we cannot know. His thought also contains Kantian elements. Kant's critique of pure reason led to a theological agnosticism, whereas his critique of practical reason led him to affirm that the realization of values follows from a person's autonomous decision. There is a tension between Leibowitz the philosopher who read Kant on human autonomy, and regarded politics and ethics as domains where human autonomy is decisive, and the halakhic man who lived in conformity with his strict halakhic, theocentric conception of Judaism. For Leibowitz, morality is thus an atheistic category. Kant's influence on Leibowitz is also clear when he states that the value of a religious act is determined by the intention. Only when one performs an act because it is a divine commandment does it posses a religious value.