Hence a certain number of efforts that characterize modern reﬂection on the sciences: the classification of thedomains of knowledge on the basis of mathematics, and the hierarchy established to provide a progression towards the more complex and the less exact; reﬂection on empirical methods of induction, and the effort made to provide them with both a philosophical foundation and a formal justification; the endeavour to purify, formalize, and possibly mathematicize thedomains of economics, biology, and finally linguistics itself.