1. A method for evaluating the operating safety of a system performing a macro function, comprising the following steps: constructing a constructed architecture of the system, divided into a plurality of blocks each comprising data inputs/outputs, the inputs of a block being connected to the outputs of other blocks of the architecture; identifying failures associated with the blocks of the architecture, the identified failures taking a state selected from a group comprising a first active state, and a second inactive state; constructing first boolean expressions expressing states of the outputs of the blocks of the architecture as a function of states of the identified failures, and of states of the inputs of the blocks, said input states of the blocks being reflected by at least one boolean; constructing one or more second boolean expressions based on the first boolean expressions, each second boolean expression defining a feared event to be examined; reducing each second boolean expression in a sum of monomials; calculating a first probability of occurrence for the feared event based on the sum of monomials, corresponding to the feared event, as a function of probabilities of occurrence of the identified failures; and changing the constructed architecture of the system in response to the first probability of occurrence of the feared event exceeding a predetermined threshold.