Baruch Spinoza (1632-1677) occupies a somewhat awkward position in the historiography of Jewish philosophy. In the standard story - or at least those versions of it that move beyond the simplistic description of how his philosophy represents a radical and heretical break from what comes before - he is presented either as the culmination of the Jewish medieval rationalist tradition (especially Maimonides and Gersonides) or as the father of modern Jewish thought, and sometimes as both. These are important (but still all too infrequently studied) perspectives for understanding Spinoza’s metaphysical, moral, and political ideas, and not just their antecedents and their legacies, but their substantive content as well. While most scholarly attention has been devoted to the seventeenth-century Cartesian background of Spinoza’s philosophy, his system also needs to be situated (as Harry Wolfson and others have recognized) in a Jewish philosophical context. But is this enough to give him a rightful place in a “Companion” to Jewish philosophy? After all, Thomas Aquinas was strongly influenced by Maimonides, and our understanding of the Summa Theologiae is deepened by a familiarity with the Guide for the Perplexed, but no one of course has ever suggested that St. Thomas is a Jewish philosopher. Does the additional fact that Spinoza, unlike Thomas, is Jewish alone qualify him for membership in the canon of “Jewish philosophers”?