Nethanel ben Moses ha-Levi was a physician at the Fatimid court, a renowned scholar, and a communal leader in twelfth-century Egypt. The Cairo Geniza has preserved a fascinating letter that Nethanel wrote to his friends as a youth. In it he complains that his father, Moses, then the “Sixth in the Society of Scholars” (i.e., the yeshiva) and a physician in the government hospital, had paid him 25 dinars, a large amount by any standard, to stay home and study rather than go out with his friends. The investment paid off: Nethanel became a famous physician and received an appointment to the …