The idea of progress is unique to the cultural tradition of Western Europe and from its birth has had a strong association with ethical issues raised by new knowledge and technological innovation. Although there are allusions to it in the twelfth and thirteenth centuries, the concept first appeared in its modern sense in the transition from the Middle Ages to the Renaissance. The idea was introduced by the early humanists in the context of their invention of the division of history into three periods: a classical age, encompassing the cultures of Greece and Rome from about 600 B.C.E. to 400 C.E.; a culturally dark "middle age" from about 400 to 1300; and their own age, self-proclaimed as a renaissance, or rebirth, of cultural excellence that began in the fourteenth century. In the seventeenth and eighteenth centuries, progress was explicitly coupled to the primacy of objective reason in human affairs...