Averroes's theory of the unity of the intellect

The unity of the intellect (also called the unicity of the intellect or monopsychism),^[1] a philosophical theory proposed by the medieval Andalusian philosopher Averroes (1126–1198), asserted that all humans share the same intellect. Averroes expounded his theory in his long commentary on Aristotle's On the Soul to explain how universal knowledge is possible within the Aristotelian philosophy of mind. Averroes's theory was influenced by related ideas propounded by previous thinkers such as Aristotle himself, Plotinus, Al-Farabi, Avicenna (Ibn Sina) and Avempace (Ibn Bajja).

Once Latin translations of Averroes's works became available in the 13th century, this theory was taken up and expanded by Averroists in the Christian West, such as Siger of Brabant (c. 1240 – c. 1284), John of Jandun (c. 1285 – 1328) and John Baconthorpe (c. 1290 – 1347). It also influenced the secularist political philosophy of Dante Alighieri (c. 1265 – 1321) in the fourteenth century. However, it was rejected by other philosophers—including Thomas Aquinas (1225 – 1274), who wrote a detailed critique—and Averroes received condemnation from Catholic Church authorities. In modern times, the theory is no longer seen as tenable; historian of philosophy Peter Adamson regards it as a product of Averroes's time.