ABSTRACT
Categories have a fundamental role to play in the production of knowledge inasmuch as they act, not just as a means of access from the empirical world to the world of science and vice versa: they act also as objects of knowledge in themselves. Theories can thus attach to categories, while categories can insert themselves into reality to become an essential part of its description. ‘The historian of science must take ideas as facts,’ wrote Bachelard, but ‘the epistemologist must take facts as ideas.’3 Categories, in the natural sciences or in law, are knowledge ideas inserted within a structure or system which itself represents an idea. This suggests of course that categories are part of the intellectus rather than the res, but this is not so. Categories are part of the relationship itself between les mots et les choses.
