Yeshayahu Leibowitz (1903-1994) was a prominent Israeli Orthodox Jewish philosopher, scientist, and public intellectual known for his polymathic contributions and incisive critiques of politics, religion, and society. Born on January 29, 1903, in Riga, Russian Empire (now Latvia), to a distinguished Jewish family, he grew up in a religiously observant environment that shaped his lifelong engagement with Jewish thought. He pursued higher education in Germany and Switzerland, studying philosophy under luminaries like Eugene Minkowski in Berlin and earning a PhD in biochemistry from the University of Basel in 1934. That same year, he immigrated to Mandatory Palestine, where he settled in Jerusalem and began his academic career. Leibowitz served as a professor of biochemistry, organic chemistry, and neurophysiology at the Hebrew University of Jerusalem, contributing significantly to scientific research while also editing the Encyclopaedia Hebraica, a major Hebrew-language reference work. His philosophical writings delved deeply into Jewish theology, ethics, and the philosophy of science, emphasizing a rational, non-mystical approach to Orthodox Judaism. He argued for the separation of religion from nationalism, viewing the latter as a corruption of true faith. As a public intellectual, Leibowitz was a prolific journalist and speaker, authoring numerous books and essays that challenged conventional wisdom. His outspoken political views made him a controversial figure in Israel. He was a fierce critic of Zionism, the Israeli occupation of Palestinian territories following the 1967 Six-Day War, and the rise of religious nationalism, warning that these would lead to moral degradation and idolatry. He advocated for a secular state and opposed the integration of religion into politics, famously proposing that Israel withdraw from occupied lands to preserve its ethical integrity. His ideas influenced a generation of activists and intellectuals, including author Amos Oz, and he remained a polarizing voice until his death on August 18, 1994, in Jerusalem.