 Having thus defined a way of measuring value we can now derive a way of measuring belief in general. If the option of [\(\omega_2\)] for certain is indifferent with that of [‘\(\omega_1\) if \(p\), \(\omega_3\) otherwise’], we can define the subject’s degree of belief in \(p\) as the ratio of the difference between [\(\omega_2\)] and [\(\omega_3\)] to that between [\(\omega_1\)] and [\(\omega_3\)]. (1926a, [FM] 179)