 Archaeology was an essential method for Foucault because it supported a historiography that did not rest on the primacy of the consciousness of individual subjects; it allowed the historian of thought to operate at an unconscious level that displaced the primacy of the subject found in both phenomenology and in traditional historiography. However, archaeology’s critical force was restricted to the comparison of the discursive formations of different periods. Such comparisons could suggest the contingency of a given way of thinking by showing that the people living in previous ages had thought very differently (and, apparently, just as effectively). But mere archaeological analysis could say nothing about the causes of the transition from one way of thinking to another and so had to ignore perhaps the most forceful case for the contingency of entrenched contemporary positions. Genealogy, the new method first deployed in Discipline and Punish, was intended to remedy this deficiency.