In his published work and even more in conversations, Tarski emphasized what he thought were important philosophical aspects of his work. The English translation of his more philosophical papers [56m] was dedicated to his teacher Tadeusz Kotarbiński, and in informal discussions of philosophy he often referred to the influence of Kotarbiński. Also, the influence of Leśniewski, his dissertation adviser, is evident in his early papers. Moreover, some of his important papers of the 1930s were initially given to philosophical audiences. For example, the famous monograph on the concept of truth ([33m], [35b]) was first given as two lectures to the Logic Section of the Philosophical Society in Warsaw in 1930. Second, his paper [33], which introduced the concepts of ω-consistency and ω-completeness as well as the rule of infinite induction, was first given at the Second Conference of the Polish Philosophical Society in Warsaw in 1927. Also [35c] was based upon an address given in 1934 to the conference for the Unity of Science in Prague; [36] and [36a] summarize an address given at the International Congress of Scientific Philosophy in Paris in 1935. The article [44a] was published in a philosophical journal and widely reprinted in philosophical texts. This list is of course not exhaustive but only representative of Tarski's philosophical interactions as reflected in lectures given to philosophical audiences, which were later embodied in substantial papers. After 1945 almost all of Tarski's publications and presentations are mathematical in character with one or two minor exceptions. This division, occurring about 1945, does not, however, indicate a loss of interest in philosophical questions but is a result of Tarski's moving to the Department of Mathematics at Berkeley. There he assumed an important role in the development of logic within mathematics in the United States.