Book excerpt: During the fourteenth century, there was a general demoralization in the Jewish community in Spain. Many Jews were on the brink of conversion. Rabbi Crescas met the Christian challenge by writing this pithy book refuting the principles of the Christian religion. He argued that the basic Christian doctrines, namely, original sin, salvation, trinity, incarnation, virgin birth, transubstantiation, baptism, the messiah, a new covenant, and demons, contradict human reason, thereby calling into question Christianity's claim to be a true religion. The Refutation is an important document of the medieval Jewish-Christian debate and is also especially important for the history of Jewish philosophy in general.