  Bruno de Finetti was one of the most convinced advocates of finitely additive
probabilities. The present work describes the intellectual pro- cess that led
him to support that stance and provides a detailed account both of the first
paper by de Finetti on the subject and of the ensuing correspondence with
Maurice Fr\'echet. Moreover, the analysis is supplemented by a useful picture
of de Finetti's interactions with the international scientific community at
that time, when he elaborated his subjectivistic conception of probability.
