Perhaps when we talk about the strenght of belief we don't have something in absolute terms, like "X is 95% sure" and "Y is 15% sure", but a hierarcy or relation, where the surest propositions (if there are such things) are defined as 100% and the most evidently false (a bachelor is a married man) as 0%, and every other belief is measured in reference to those two. I prefer the latter. — Lionino

A parallel tradition, though never as dominant, holds that degrees of belief are neither so precise, nor as definitely comparable as suggested by Pascal's probabilistic analysis. Keynes (1921) famously proposed that degrees of belief may enjoy only an ordinal structure, which admits of qualitative, but not quantitative, comparison. Keynes even suggests that the strength of some pairs of partial beliefs cannot be compared at all.

Cohen (1980) traces another minority tradition to Francis Bacon's Novum Organum (1620/2000). On the usual probability scale a degree of belief of zero in some proposition implies maximal conviction in its negation. On the Baconian scale, a degree of belief of zero implies no conviction in either the proposition or its negation. Thus, the usual scale runs from “disproof to proof” whereas the Baconian runs from “no evidence, or non-proof to proof.” In the past few decades, Baconian probability has received increasing attention, resulting in theories approaching the maturity and sophistication of those in the Pascalian tradition (Spohn, 2012, Huber, 2019). — SEP