In the context of history as an academic field, the word "theory" is more often used to refer to the overarching perspectives we construct while carrying out research. But even in this context we may use the term at different conceptual levels. A fundamental theoretical question concerns the actual nature of historical knowledge: is the past a given quantity that historians should describe as realistically as possible, or is the writing of history a matter of constructing a past that only exists in the form of language and representational images? More concretely, a theory can be a view of history, an opinion about the fundamental nature of those aspects of the past that we wish to present. For example, a historical materialist will be interested in labour, production and the economy, while a structuralist will try to describe common basic structures in language and thinking. Such theoretical perspectives will be decisive with regard to a historian's choice of sources, research topics and view of historical knowledge, but they will seldom be mutually exclusive. In practice, history is a field where pragmatic attitudes to theory prevail.