abu sina) (980-1037. Persian Muslim philosopher. Born in Bokhara, he was a voluminous commentator on Aristotle. A versatile man, his Canon was the standard medical textbook for five centuries in Europe and beyond. Like other Arabic Aristotelians, he helped restore to Judaism and Christendom that Greek learning which had been lost in the Dark Ages. He gave Aristotle a Neoplatonic twist, with his nine descending mediating Intelligences between deity and man, the ninth occupying the lunar sphere. He postulated an eternal universe, with an inbuilt necessity system and a remote deterministic God debarred from direct creative action. Science, metaphysics, and theology are deeply indebted to Avicenna; Dante mentions him respectfully (Inferno iv, 143). He was an eclectic thinker in whose work experts detect unresolved internal inconsistencies. He has been charged with originating a disreputable compromise doctrine of twofold truth to harmonize reason with revelation, which introduces a double standard before which all intellectual integrity would finally crumble.