By the mid 20th century there were a number of structural theories of human existence. In the study of language, the structural linguistics of Ferdinand de Saussure (1857-1913) suggested that meaning was to be found within the structure of a whole language rather than in the analysis of individual words. For Marxists, the truth of human existence could be understood by an analysis of economic structures. Psychoanalysts attempted to describe the structure of the psyche in terms of an unconscious.
In the 1960's, the structuralist movement, based in France, attempted to synthesise the ideas of Marx, Freud and Saussure. They disagreed with the existentialists' claim that each man is what he makes himself. For the structuralist the individual is shaped by sociological, psychological and linguistic structures over which he/she has no control, but which could be uncovered by using their methods of investigation.
Originally labelled a structuralist, the French philosopher and historian Michel Foucault came to be seen as the most important representative of the post-structuralist movement. He agreed that language and society were shaped by rule governed systems, but he disagreed with the structuralists on two counts. Firstly, he did not think that there were definite underlying structures that could explain the human condition and secondly he thought that it was impossible to step outside of discourse and survey the situation objectively.
Jacques Derrida (1930- ) developed deconstruction as a technique for uncovering the multiple interpretation of texts. Influenced by Heidegger and Nietzsche, Derrida suggests that all text has ambiguity and because of this the possibility of a final and complete interpretation is impossible.
The postmodern subject has no rational way to evaluate a preference in relation to judgements of truth, morality, aesthetic experience or objectivity. As the old hierarchies of thought are torn down, a new clearing is formed on the frontiers of understanding: quite what hybrids of thought will metamorphose, interbreed and grow is this clearing is for the future to decide.
In his latter work, he borrowed from Nietzsche the 'genealogical' approach and from Marx his analyses of ideology. Foucault sought to show how the development of knowledge was intertwined with the mechanisms of (political) power. Unlike Marx, Foucault had no underlying belief in a deep underlying truth or structure: there was no objective viewpoint from which one could analyse discourse or society.
Foucault focused on the way that knowledge and the increase of the power of the state over the individual has developed in the modern era. In his 'History of Sexuality' he argued that the rise of medical and psychiatric science has created a discourse of sexuality as deep, instinctual and mysterious. This discourse became accepted as the dominant explanation, and its assumptions began to seep into the discourse of the everyday. In this way the human subjects's experience of their own sexuality is shaped and controlled by the discourses that purport to explain it. The search for knowledge does not simply uncover pre-existing 'objects'; it actively shapes and creates them.
Foucault does not offer any all-embracing theory of human nature. He was critical of 'meta-theory': beliefs that claimed to give an exclusive objective explanation of reality. For Foucault there is no ultimate answer waiting to be uncovered. The 'discursive practices' of knowledge are not independent of the objects that are studied, and must be understood in their social and political context.
Derrida thought that all text contained a legacy of these assumptions, and as a result of this, these texts could be re-interpreted with an awareness of the hierarchies implicit in language. Derrida does not think that we can reach an end point of interpretation, a truth. For Derrida all text s exhibit 'differance': they allow multiple interpretations. Meaning is diffuse, not settled. Textuality always gives us a surplus of possibilities, yet we cannot stand outside of textuality in an attempt to find objectivity.
One consequence of deconstruction is that certainty in textual analyses becomes impossible. There may be competing interpretations, but there is no uninterpreted way one could assess the validity of these competing interpretations. Rather than basing our philosophical understanding on undeniable truths, the deconstructionist turns the settled bedrock of rationalism into the shifting sands of a multiplicity of interpretations.