Degrees of Belief. Third, probability is about degrees of belief. A degree of belief can be based on anything from experience to personal impression. Historically, its origin is in eyewitness testimony in courts and, more spectacularly, in the Judeo-Christian lore of miracles.11 To this day, the testimony of two independent witnesses counts more than that of two who talked with each other beforehand, and the same holds for the testimony of a witness who did not know the defendant than that of his brother.
