Natural Right and History is widely recognized as Strauss's most influential work. The six lectures, written while Strauss was at the New School, and a full transcript of the 1949 Walgreen Lectures show Strauss working toward the ideas he would present in fully matured form in his landmark work. In them, he explores natural right and the relationship between modern philosophers and the thought of the ancient Greek philosophers, as well as the relation of political philosophy to contemporary political science and to major political and historical events, especially the Holocaust and World War II. Previously unpublished in book form, Strauss's lectures are presented here in a thematic order that mirrors Natural Right and History and with interpretive essays by J. A. Colen, Christopher Lynch, Svetozar Minkov, Daniel Tanguay, Nathan Tarcov, and Michael Zuckert that establish their relation to the work. Rounding out the book are copious annotations and notes to facilitate further study.