Imam Abu Hamid al-Ghazali is one of the most influential thinkers of medieval Islam. His writings on the interrelation of law, theology and mysticism were central in establishing Sufism as a core dimension of orthodox Islamic practice. Today, many Muslim communities still base much of their practice of Islam on Ghazali’s writings. The Forty Foundations of Religion, Ghazali’s own summary of his best-known work, The Revival of the Religious Sciences, outlines the basis of Islamic belief, ritual, and practice.