 He belonged to the well-known Nathan family, which claimed its descent from David; he was probably the grandson of the translator Maestro Bongodas Judah Nathan.According to the statement of Isaac himself, in the introduction to his concordance (see below), he was completely ignorant of the Bible until his fifteenth year, his studies having been restricted to the Talmud and to religious philosophy.Later he took up other branches of learning, and owing to his frequent association with Christians and to the numerous anti-Jewish writings of Jewish apostates that appeared at that time, he turned his attention to religious controversy.