Criterio di penalizzazione e condizioni di coerenza nella valutazione soggettiva della probabilità

In this paper the coherence condition based on the penalty criterion, proposed by de Finetti in his subjective theory of probability, is examined. Then a 'slight' modification of this definition of coherence, which is equivalent, when applied to nonconditional events, to that of de Finetti, is studied. Contrary to the latter, our definition does not require, in the case of conditional events, any strengthening. This more 'natural' condition (called C_0 coherence) is also interpreted from a geometrical point of view by means of a generalization of the concept of constituent. Moreover, we show the equivalence between the strengthened coherence based on the betting criterion and C_0 coherence.