In historiography, progress (from Latin progressus, “an advance”) is the study of how specific societies improved over time in terms of science, technology, modernization, liberty, democracy, longevity, quality of life, freedom from pollution and so on. Specific indicators can range from economic data, technical innovations, change in the political or legal system, and questions bearing on individual life chances, such as life expectancy and risk of disease and disability. Many high-level theories, such as the Idea of Progress Are available, such as the Western notion of monotonic change in a straight, linear fashion. Alternative conceptions exist, such as the cyclic theory of eternal return, or the “spiral-shaped” dialectic progress of Hegel, Marx, et al.