Even more than the above, the expressions of informal mathematics discourse have implicit meanings associated with the overall background theory and context. For the rules and meanings which govern such expressions do not have precise formal stipulations, but depend even more on implicit rules of use (Wittgenstein, 1953). Models of the semantics of both formal and informal languages increasingly draw on the context of utterances (Barwise and Perry,1982). Whether expressed in formal or informal language, the expressions of mathematics cannot be regarded as free standing, independent bearers of meaning. Thus mathematics cannot be represented simply as a set of ‘molecular’ propositions, for these do not represent the structural relationships between propositions, as well as losing their context – dependent meanings.