Illuminationism is a Medieval school of Islamic philosophy founded in the 12th Century by Shahab al-Din Suhrawardi (1155 - 1191). It is a combination of Avicennism and ancient Persian philosophy, along with many new innovative ideas of Suhrawardi himself. He is often described as influenced by Neo-Platonism in that he attempted a synthesis of Platonic, Zoroastrian and Islamic ideas.
Suhrawardi was a Sufi (a mystical sect of Islam). He was critical of several of the positions taken by Avicenna, and radically departed from him through the creation of a symbolic language derived from ancient Iranian culture.
The fundamental constituent of Suhrawardi’s philosophy is pure, immaterial light, which unfolds from the "light of lights" in emanations through the descending order of the light of ever-diminishing intensity. Through complex interaction, this in turn gives rise to horizontal arrays of lights, similar in concept to Platonic Forms (see the section on Platonic Realism), which govern the different types of mundane reality. Thus, it views the whole of reality as a continuum, with the physical world being an aspect of the divine. Suhrawardi also elaborated the idea of an independent, intermediary world, the imaginal world.
Illuminationist philosophy challenges the Aristotelian position of the absolute, unchanging and universal validity of truths, and argues that a conclusion reached by using a formally established syllogism has no epistemological value as a starting point in philosophical construction. It emphasizes intuitive knowledge (as opposed to acquired or representational knowledge), and attempts to unravel the mysteries of nature through the metaphysical world of myths, dreams, fantasy and inspiration, rather than through the principles of physics. It supports the idea of "essence precedes existence" previously espoused by Avicenna and his school of Avicennism, and opposed by Averroism and later by Mulla Sadra (c. 1571 – 1640) and his Transcendent Theosophy movement.
In the 17th Century, Illuminationism initiated a Zoroastrian revival in the figure of Azar Kayvan (1533 - 1618), but in its original form it has remained an important force in Islamic, especially Persian, philosophy right up to the present day.