Philosophers 'do' 'it', literary critics 'do' 'it', even architects and psychoanalysts 'do' 'it', poets 'do' 'it', painters 'do' 'it', capital and the political are said to 'do' 'it', texts 'do' 'it' to themselves and justice is 'it', but what is this thing? The following pages are an introduction to the term which has come to act as a metonym for the work of Jacques Derrida and the substantial body of knowledge which has grown up around his texts in the form of an extensive commentary and dialogue. However, the word means more than this. It is a translation (and adaptation) into French, and then into the languages of the world, of the Heideggerian term 'Destruktion' or 'Abbau'. In this sense it suggests an operation performed in relation to the structure of the fundamental concepts of Western metaphysics. It is a translation- successful or not - which attempts to limit the connotations of 'destruction' implied by a straight transliteration of Heidegger's term into French. In French, it has both a grammatical and a mechanical meaning. It means both to disarrange the construction of words in a sentence and to disassemble a machine and transport it elsewhere. It also forms a reflexive verb [se deconstuire] meaning to lose one's own construction. However, this thing can not be reduced to a semantic or a mechanical model. Indeed the term itself questions the architecture of such models, as well as the model of architecture.