Ibn Khaldun

Ibn Khaldun of Tunis — descendant of Andalusian exiles, minister and sometime prisoner of half the courts of the Maghreb, later chief Maliki judge in Cairo — withdrew to a castle in Algeria in 1375 and wrote the Muqaddimah, the "Introduction" to a universal history that founded a science no one had imagined: the study of human society itself, ilm al-umran.

States, he observed, behave like organisms. The engine is asabiyyah — group solidarity, the fierce cohesion of desert and mountain peoples — which conquers cities, founds dynasties, and is then dissolved by the very luxury it wins: within roughly four generations, hardy founders become taxed, softened heirs, and a fresher solidarity from the periphery takes their place. His economics anticipated moderns by centuries: excessive taxation shrinks revenue by killing enterprise; prices, labor, and profits move by supply and demand; the sovereign's seizures destroy the incentive on which civilization runs.

He is equally the founder of source criticism in history. The Muqaddimah opens by cataloguing why historians lie — partisanship, credulity, ignorance of the natures of things — and lays down the rule that reports must be tested against the possible: "the normative method for distinguishing right from wrong in historical information... is to investigate whether it is possible that the event can have happened."

Religion in his system is a real historical force with a natural mechanics: prophecy succeeds when it harnesses asabiyyah (Islam's conquests being his prime case), and religious solidarity doubles a dynasty's power — an analysis pious and coldly empirical at once. In 1401 he was lowered from Damascus's walls to parley with Tamerlane, who questioned him for weeks: the theorist of empire face to face with the thing itself. Toynbee called the Muqaddimah "the greatest work of its kind that has ever yet been created by any mind in any time or place."