The study of the social origins of belief systems and (according to its proponents) knowledge. The German political philosophers Karl Marx (1818–83) and Friedrich Engels (1820–95) argued in Die Deutsche Ideologie (1846, The German Ideology) and elsewhere that people's ideologies, including their social and political beliefs and opinions, are rooted in their class interests, and more generally in the social and economic circumstances in which they live: ‘It is men, who, in developing their material intercourse, change, along with this their real existence, their thinking and the products of their thinking. Life is not determined by consciousness, but consciousness by life’ (Marx-Engels Gesamtausgabe 1/5). Under the influence of this doctrine, and of phenomenology, the Hungarian-born German sociologist Karl Mannheim (1893–1947) gave impetus to the growth of the sociology of knowledge with his Ideologie und Utopie (1929, translated in 1936 as Ideology and Utopia), although the term had been introduced five years earlier by the co-founder of the movement, the German philosopher and social theorist Max Scheler (1874–1928), in Versuche zu einer Soziologie des Wissens (1924, Attempts at a Sociology of Knowledge). A strong interpretation claims that all knowledge and beliefs are the products of socio-political forces, but this version is self-defeating, because if it is true, then it too is merely a product of socio-political forces and has no claim to truth and no persuasive force. Mannheim sought to escape this paradox by exempting free-floating intellectuals, whom he claimed were only loosely anchored in social traditions, relatively detached from the class system, and capable of avoiding the pitfalls of total ideologies and of forging a ‘dynamic synthesis’ of the ideologies of other groups. See also epistemology, sociology.