Belief in progress is the belief that later times are improvements over earlier times. This may be in limited respects, such as in the extent of scientific knowledge or some of the moral capacities of human beings. Or the improvement may be more global, as in the world view of Hegel who sees history as the progressive embodiment of rational principles. The 18th century (Voltaire, Condorcet, Kant) saw the greatest flowering of belief in progress, with belief that a benevolent providence had secured for us perfectibility on earth, through increasing deployment of knowledge and reason. In the 19th century belief in progress continued to flourish, with Comte and Marx equally enamoured of it. The theory of evolution through natural selection added (spurious) support to the idea in the work of social evolutionists such as Spencer. The progressive nature of scientific enquiry is probably the most impressive example of progress that we have, although even this is doubted by philosophies of a sceptical and relativistic bent, that see in science only a history of revolutions. See also perfectibility.