Saadia Gaon

The absence of an explicit prohibition in the Torah against father-daughter incest led to a debate among the talmudic-era rabbis, and eventually among medieval Rabbanites and Karaites, about whether such a prohibition should be derived from a logical a fortiori (קל וחומר) argument or from a hermeneutic (גזרה שוה) one.

Gedaliah ben Ahikam, the governor of Judah after the destruction of the Temple, was assassinated by Ishmael ben Nethaniah, a scion of the Davidic family. This event has been commemorated for millennia with a yearly fast—the only fast over the death of an individual. The Talmud points to his righteousness, while Saadia Gaon emphasizes the tragic consequences to the Judahite people he governed.

Betuel, Rebecca’s father, mysteriously appears and disappears in the negotiations over Rebecca’s marriage.

The nature of prophecy is perhaps one of the most overlooked questions, but it was critically important to the medieval Jewish philosophers Sa’adia Gaon, Judah Halevi, Ibn Ezra, and Maimonides.

The development of the idea that the Torah has 613 mitzvot: From Talmudic aggada, to geonic liturgy, to medieval enumerations.