Muhammad b. Abd al-Karim al-Shahrastani was one of the most learned and enigmatic scholars of medieval Islam. In his work, 'Kitab al-Musara'a' ('Struggling with the Philosopher'), which is published here in English translation (together with its original Arabic text) for the first time, al-Shahrastani gives a detailed critique of the metaphysics of the great Persian philosopher Avicenna. The greater part of his 'intellectual wrestling match' ('musara'a') is devoted to refuting Avicenna's interpretation of the 'Necessary Being' which, he argues, compromises the absolute transcendence of God. For al-Shahrastani, God is beyond human comprehension and above all opposites such as existence and non-existence, unity and multiplicity, good and evil, or truth and falsehood. This work is a strong indication of the rich diversity and eclecticism that characterised intellectual discourse in medieval Islam. 'Struggling with the Philosopher' is an important document of Islamic intellectual history. As such, it is essential reading and a reference text for students of Islamic studies and scholars interested in the medieval Islamic world.