The SF rule of classical probability: an exploration of the "gambler's paradox"

This paper uses the "gambler's paradox", an event of classical probability origin, as an entry point, and use graphical and observational methods to generalize the SF rule. The SF rule is used to explain the compound events, to demonstrate the formal guarantee of the SF rule, and to deduce the detailed steps of using the SF rule. As an important rule for selecting basic events in classical probability, the SF rule should be described in the probability foundation.