The great intellectual tradition that comes down to us from the past was never interrupted or lost through such trifles as the sack of Rome, the triumph of Attila, or all the barbarian invasions of the Dark Ages. It was lost after the introduction of printing, the discovery of America, the founding of the Royal Society, and all the enlightenment of the Renaissance and the modern world. It was there, if anywhere, that there was lost or impatiently snapped the long thin delicate thread that had descended from distant antiquity; the thread of that unusual human hobby: the habit of thinking.