Drawing on Foucault the author tries to answer the questions such as What is actually an event?, What is it that makes an usual phenomenon an event?, What is it that makes a historical event to emerge out of a set of banal events? It is evident, that the answers to these questions depend on the general view of history. Foucaultian history is nominalistic, i. e. stressing the uniqueness of historical event. The latter is never isolated, but together with other events creating a net with an intrinsic structure. This structure determines the status or order and meanings of particular events and sheds light on the critical role of one of these events. And vice versa: due to this critical historical event a contingent set of events becomes structured and ordered. An illustration is Foucaultś analysis of the origin of insanity as a mental illness.