Jewish polemics and apologetics in the Middle Ages
Jewish polemics and apologetics in the Middle Ages were texts written to protect and dissuade Jewish communities from conversion to Christianity, or more rarely to Islam. The terms polemics and apologetics may be distinguished but may also be considered somewhat subjective. A smaller number of proselytizing text also exists intended to convert Christians, or more rarely Muslims, to Judaism.
Under the pre-Christian and Christianizing Roman Empire
During the Middle Ages many polemical texts originated outside Catholic Europe in lands where Jews and Christians were on an even footing as subjects of Islam. Among the oldest anti-Christian texts with polemic intent is the Toledot Yeshu "Life of Jesus", although this does not follow the reasoned format of argument found in a true polemic or apologetic work. The earliest true polemic is the Sefer Nestor Ha-Komer "The Book of Nestor the Priest". The book represents itself as the arguments for Judaism of a former Christian priest. The need for apologetics emerged as national boundaries were in flux. Saadia's Kitab al-Amanat wal-I'tikadat "Book of Belief and Opinions" includes refutations of the Christian Trinity, and more restrainedly against Hiwi al-Balkhi's arguments against the Jewish scriptures. The Cairo Genizah fragments include polemics against Samaritans, Christianity, and Islam, as well as Jewish sects, from the early 10th century. Both Jews and Christians under Islam were careful in criticism of, or proselytizing to, their host's religion, in response to Muslim proselytzing of Jews and Christians. Judah Halevi's Arabic Kitab al Khazari "Book of the Khazars", subtitled "The book of refutation and proof on behalf of the despised religion," included apologetics to Islam alongside Christianity and Greek philosophy.
In Catholic Europe
Jews in Europe began to write polemical works in the 12th century. The Milhamoth ha-Shem "Wars of the Name" of Jacob ben Reuben is an apologetic text against conversion by Christians, notable in that it contains questions and answers based on selected Hebrew translations of the Latin Gospel of Matthew and appears to have served as a precedent for the full Hebrew translation and interspersed commentary on Matthew found in Ibn Shaprut's Touchstone. Joseph Kimhi's Sefer ha-Berit "Book of the covenant" follows Jacob ben Reuben's format of an apologetic response to Christian argument, but does not only refute Christian challenges, Kimhi also identifies weaknesses of Christian belief. Around the same period are the Sefer Nizzahon Yashan "The Book of Victory" a "typical Ashkenazic polemic," and the Sefer Joseph Hamekane "Book of Joseph the Official" of rabbi Joseph ben Nathan which presents among other arguments a conversation between a Christian, the 'Chancellor,' and two rabbis. Other apologetic works include Joseph Albo's Sefer Ha-Ikkarim "Book of Principles", Chasdai Crescas' Or Adonai "Light of the Lord", Isaac of Troki's Hizzuk emunah "Faith strengthened".