Professor Michael Lessnoff, University of Glasgow, presents that Ernest Gellner’s analysis of Islam was shaped by his theory of history and of modernity. Modern industrial society, for Gellner, rests on and demands a uniform, literate (i.e. “high”) culture: pre-modern agricultural society was fragmented into a literate “high” culture and illiterate “folk” cultures. In Islam, Gellner argued, the central literate high culture was and is in a generic sense very “Protestant” and therefore (unlike other non-Western traditional cultures) well suited to modernity: hence its present strength. But in fact traditional Islamic high culture was divided between puritan orthodox and Sufi mystic variants; and the former is in spirit profoundly anti-modern – more so, arguably, than the Sufi alternative, which nurtured the great scientific culture of medieval Islam. Science is a defining element of Gellnerian modernity, but Islamic science never became modern science. Prof. Michael Lessnoff shall try to suggest why not, through comparison with the Western case.