Since the 1950s a new social theory has emerged which shares many of the holistic assumptions of functionalism and Marxism. Originating in the study of languages, structuralism has exerted an enormous influence in the social sciences especially in the work of Lévi-Strauss (anthropology), Roland Barthes, Julia Kristeva (semiotics and literary theory), Althusser, Poulantzas (Marxism and sociology) Godelier (economics), Foucault (philosophy and the history of science), and Lacan (psycho-analysis). Although these theorists disagree about the exact nature of structuralism there is, nevertheless, a broad consensus that a structuralist approach to the study of human society and culture involves the notion of wholes (a structure is not a simple aggregate of elements), the idea of transformation (structures are dynamic, not static, governed by laws which determine the ways that new elements are introduced into the structure and changed) and the concept of self-regulation (the meaning of a structure is self-contained in relation to its internal laws and rules). Where structuralism differs from functionalism and positivist Marxism is in its rejection of objective social facts and a concept of society as an objective, non-problematic external datum. Social facts have to be reconstituted in a theoretical discourse if they are to have any meaning at all. In short, structuralism defines reality in terms of the relations between elements, not in terms of things and social facts. Its basic principle is that the observable is meaningful only in so far as it can be related to an underlying structure or order.