The medieval Islamic world comprised a wide variety of religions. While individuals and communities in this world identified themselves with particular faiths, boundaries between these groups were vague and in some cases nonexistent. Rather than simply borrowing or lending customs, goods, and notions to one another, the peoples of the Mediterranean region interacted within a common culture. Beyond Religious Borders presents sophisticated and often revolutionary studies of the ways Jewish, Christian, and Muslim thinkers drew ideas and inspiration from outside the bounds of their own...