Progress

History has a direction, and it runs toward better. The Enlightenment was the first age to believe this, and to treat it as a reason to act.

Ancient and medieval thought largely imagined history as cyclical or as a fall from a golden age. The Enlightenment reversed this: Turgot, Condorcet, and Diderot argued that knowledge accumulates, that science improves life, and that humanity is on a trajectory toward greater freedom and happiness. The Encyclopedie was itself a monument to this belief, an attempt to record everything humanity had learned so far and make it available to everyone. Progress was not inevitable but possible, and philosophy's task was to accelerate it. The idea was revolutionary. It was also, as subsequent history showed, more complicated than it appeared.