ʿAyn al-Quḍāt (d. 525/1131) was a philosopher, mystic, and judge who was born in the western Iranian city of Hamadān. He was the student of Aḥmad al-Ghazālī (d. 520/1126), the brother of the famous Abū Ḥāmid al-Ghazālī (d. 505/1111). A maverick figure, he was put to death by the Seljuqs at the age of thirty-four, ostensibly on charges of heresy. Livia Kohn is Professor Emerita of Religion and East Asian Studies at Boston University. She is the author of Sitting in Oblivion: The Heart of Daoist Meditation. Mohammed Rustom is Professor of Islamic Studies at Carleton University. An internationally recognized scholar whose works have been translated into over ten languages, he specializes in Sufism, Islamic philosophy, and Qurʾanic exegesis. He is author of The Triumph of Mercy: Philosophy and Scripture in Mullā Ṣadrā and Inrushes of the Heart: The Sufi Philosophy of ʿAyn al-Quḍāt; co-editor of The Study Quran: A New Translation and Commentary; and translator of Abū Ḥāmid al-Ghazālī's Condemnation of Pride and Self-Admiration.

"Rustom's new book is a masterful translation, superb critical edition and comprehensive guide to the thought of one of the most prominent Muslim thinkers." - Islam and Christian-Muslim Relations"The Essence of Reality is a clear and fluent translation that successfully transfers the literary power of the original text into English." - Nazariyat "[Rustom's] translation strikes a delicate balance between faithfulness to the Arabic original and readability for a wide audience… A historical classic brought back to life by Rustom's able skills as translator and commentator." - Marginalia, Los Angeles Review of Books"Like many readers of Arabic Sufi writings, I have always felt that translations of Sufi texts often miss the subtle beauty of the original Arabic. […] Reading The Essence of Reality, I now have a new standard of judgment. […] There is no doubt that The Essence of Reality represents a major feat in the field of Sufi studies." - Journal of Islamic and Muslim Studies