Abu Hamid Muhammad al-Ghazali's philosophical explorations covered nearly the entire spectrum of twelfth-century beliefs. Beginning his career as a skeptic, he ended it as a scholar of mysticism and orthodoxy. The Niche of Lights, written near the end of his illustrious career, advances the philosophically important idea that reason can serve as a connection between the devout and God. Al-Ghazali argues that abstracting God from the world, as he believed...