As Bruno de Finetti taught us, the notion of event in a theory of probability is fundamental, perhaps determinative. In this paper, I compare the notion of event in de Finetti's subjective theory of probability with the more situated notion of event that underlies the theory of probability and causality that I developed in the 1990s. This text was prepared for talks in Pisa, March 14, 2001, and Bologna, March 15, 2001. [ABSTRACT FROM AUTHOR]