AbstractThe author first investigates how to precise and get to the core of the sense of a word in common language. Any definition, however appropriate it may seem, is in fact inadequate. The word must be considered as a moment of a precising activity, which is particularly clear in the case of analogy as a word and an idea. With that in view, the concept of the scheme is explained and it is examined in which horizon a mental scheme may have an existence of its own. In order to provide a satisfactory answer, it is necessary to investigate and uncover the structure of subjectivity, to make it understood that the basic principles of mathematics arise from elaborating some of these disciplines in relation with a scheme.Two fields of existence may then be said analogous if they may be considered as two different realisations of a scheme. The views gained in investigating the structures of subjectivity permit to realize (1) how the result may be extended to mathematical models and (2) how the part played by those mathematical models may be precised.