This chapter presents the sources of the arguments which are the components of the Jewish philosophical critique of Christianity in the Middle Ages. The one genre of literature in which most of these contentions are located is the polemic. The Jewish polemical works exhibit great diversity both in method of argumentation and in style. According to Joseph ben Shem Tov, there are six types of polemical treatises. The first, and by far the largest, category contains works which dealt primarily with the exegesis of the Hebrew Bible. The other categories include the exegesis of rabbinic literature; attacks on Christianity; comparisons of Christian doctrines with the New Testament; attacks on the articles of Christianity; and comparisons of Christianity with the Principles of Philosophy. Jewish polemicists also employed a variety of forms in which to place their polemics. The most common forms were the dialogue or disputation; the expository treatise, following either the biblical or a topical arrangement; the poem; the letter; and the parody. The chapter then looks at other sources of Jewish philosophical arguments, such as biblical commentaries, mysticism, and legal works. It also considers the sources of Christian polemics.