Sadr al-Din Shirazi (d. 1050/1640), known as Mulla Sadra and Sadr al-Muta'allihin , was the philosopher who, after centuries of philosophical development in Islam, brought complete order and harmony into the discussion of philosophical problems for the first time. He organized and systematized them like mathematical problems and at the same time wed philosophy and gnosis, thereby bringing about several important developments. He gave to philosophy new ways to discuss and solve hundreds of problems that could not be solved through Peripatetic philosophy. He made possible the analysis and solution of a series of mystical questions which to that day had been considered as belonging to a domain above that of reason and beyond comprehension through rational thought. He clarified and elucidated the meaning of many treasuries of wisdom, contained in the exoteric sources of religion in the profound metaphysical utterances of the Imams of the Household of the Prophet, that for centuries had been considered as insoluble riddles and usually believed to be of an allegorical or even unclear nature. In this way gnosis, philosophy and the exoteric aspect of religion were completely harmonized and began to follow a single course.
By following the methods he had developed, Mulla Sadra succeeded in proving "transubstantial motion" (harakat-i jawhariyah) , and in discovering the intimate relation of time to the three spatial dimensions in a manner that is similar to the meaning given in modern physics to the "fourth dimension" and which resembles the general principles of the theory of relativity (relativity of course in the corporeal world outside the mind, not in the mind), and many other noteworthy principles. He wrote nearly fifty books and treatises. Among his greatest masterpieces is the four-volume Asfar.
It should be noted here that before Mulla Sadra certain sages like Suhrawardi, the 6th/12th century philosopher and author of Hikmat al-ishraq , and Shams al-Din Turkah, a philosopher of the 8th/14th century, had taken steps toward harmonizing gnosis, philosophy and exoteric religion, but credit for complete success in this undertaking belongs to Mulla Sadra.