Is multiculturalism compatible with laicism? And what about nationalism? In order to answer this question it’s obviously compulsory to define all these terms, but in particular to clarify what we mean by laicism, a term which seems to be out of question as one of the rule of law strongest bases. The essay offers a strong and demanding definition of laicism which is used from a critical perspective to show how weak and contradictory some concepts which belong to the most used definition of multiculturalism and nationalism are. From the same perspective the relationships which link these two «isms» are analyzed: far from being in theoretical opposition, multiculturalism and nationalism seem to the author as two levels in which the same organic and historicist conception of society comes out, which enphasizes common sense and tradition with respect to critical knowledge and public use of reason.