Conditional events in probability assessment and revision

By resorting to the general interpretation of an event as a proposition, we deal with its natural generalization, the concept of conditional event. No algebraic structure is put on the given family of conditional events. An important feature of our approach is that conditional probability makes sense also when the conditioning event is null. Our attention is centered on de Finetti´s approach to probability, whose distinguishing features make it particularly flexible for application to both artificial intelligence and inferential statistics. In particular, the problem of comparing null events by means of conditional events is considered: so the need for the introduction of iterated conditioning naturally arises when we try to compare conditional events of zero conditional probability