It is commonly held that Islamic philosophy ended with al-Ghazali's critique and the death of Averroes; that is partly true for the western, Arabic-writing wing and false for Iran. In the east the tradition continued through Suhrawardi's philosophy of Illumination and reached a new height in Safavid Iran in the sixteenth and seventeenth centuries as the School of Isfahan. Sadr al-Din Shirazi — Mulla Sadra — is its greatest figure, and taught at the Khan Madrasa in Shiraz.

His system is called al-Hikma al-muta'aliya, Transcendent Wisdom. Two theses stand at its centre. The first is *asalat al-wujud*: what is real is existence, while essence is a section the mind abstracts from it — reversing the debate over existence and essence running since Avicenna. Existence is a single reality that intensifies by degrees; stone, plant, human and angel are different intensities of the same being. The second is *al-haraka al-jawhariyya*, substantial motion: where the Aristotelian tradition allowed motion only in qualities, Sadra argues that substance itself changes continuously. The world is then not a stock of static substances but a constant becoming, and the soul's beginning with the body and gradual movement toward abstraction is explained by the same motion.

His method matters as much as his theses: demonstration, mystical intuition and revelation are all admitted as legitimate sources of knowledge within one framework. For this he drew criticism from philosophers and Sufis alike and withdrew for a period into something close to exile. His teaching continued without interruption as part of the madrasa curriculum in Iran and kept a central position in twentieth-century Iranian thought, from Tabataba'i onward. In the West he became known only in the later twentieth century, largely through the work of Henry Corbin.