(1533–1594; according to others: 1525–1586), Karaite scholar who was born and lived in the Lithuanian town of Trakai. Yitsḥak ben Avraham wrote several compositions on Karaite ritual law (a collection of responsa on ritual slaughter is attributed to him), composed versed prayers, served as a dayan (judge) for both the Karaite and Rabbinite Jewish communities of Trakai, and served for a year as secretary to the Karaite Council of Lithuania.
Troki is recalled mainly for his book Ḥizuk emunah, a polemical composition in defense of Judaism against Christian biblical exegesis—a central theme of Jewish–Christian polemic in Eastern Europe until the second half of the seventeenth century. Ḥizuk emunah was the only such composition written from the Jewish perspective in that region before the eighteenth century. Yitsḥak ben Avraham knew not only Hebrew and Yiddish and Jewish traditions, but also Polish, Latin, and contemporary Christian theological literature. He was therefore able to polemicize with Christian clerics of different denominations, particularly the so-called Arians (Unitarians or Socians), especially Szymon Budny and Marcin Czechowicz.
In Ḥizuk emunah, Troki methodically refutes the Christian interpretation of biblical prophecies as references to Jesus’ messianic mission. He follows this with an argument against the divinity of Jesus, a comparison between the Hebrew Bible and the Gospels, and an analysis of the contradictory nature of the Christian accusation against Jews over Jesus’ crucifixion. He concludes his book with a discussion of Jewish–Christian relations during his own age, and claims that various wars and disasters in Christian countries were divine punishments for the persecutions of Jews.
Yitsḥak ben Avraham did not complete his book during his lifetime, so his student Yosef Malinowski (d. after 1624) supplemented it with an introduction and index, in which form Ḥizuk emunah began to circulate in manuscript. It was, in fact, characteristic for polemical texts not to be published but to circulate in this form. The work was published for the first time, together with a Latin translation, by the Hebraist Christian Wagenseil in his Tela ignea satanae (1681). For Wagenseil, the work by Troki was evidence of Jewish hostility to Christianity. The first publication of Ḥizuk emunah under Jewish auspices was in Amsterdam in 1705. It was later translated into Yiddish, German, and English.
Ḥizuk emunah does not cite Karaite sources, but its canonical Rabbinite authorities include the Babylonian Talmud, Rashi, Maimonides, Abravanel, and many others. This likely explains its adoption in Rabbinite circles. Some of the arguments found in Ḥizuk emunah also served anticlerical writers of the Enlightenment movement in the eighteenth century (such as Voltaire, who mentioned it as an exemplary piece of scholarship).
Jacob Mann, Texts and Studies in Jewish History and Literature, vol. 2 (New York, 1935); Judah M. Rosenthal, “Marcin Czechowicz and Jacob of Belzyce: Arian-Jewish Encounters in 16th century Poland,” Proceedings of the American Academy for Jewish Research 34 (1966): 77–97; S. Schreiner, “Isaac of Traki’s Studies of Rabbinic Literature,” Polin 15 (2002): 65–76; M. Waysblum, “Isaac of Troki and Christian Controversy,” Journal of Jewish Studies 3 (1952): 62–77.