He was born in Nicomedia. While little is known about his personal life, he is considered by Karaites to be the equivalent of his contemporary, Maimonides, the most distinguished Jewish scholar of the time and an outspoken critic of the Karaites. In fact, it seems likely that Aaron made it his ambition to rival Maimonides by defending the Karaites from his attacks. To achieve this, he studied the extensive religious literature of both rabbinical Judaism and Islam, as well as that of the Karaites.