The measurement of belief

Chapter 4 addresses objections that precise numerical probabilities are psychologically implausible or computationally intractable. Easwaran responds using measurement theory: just as temperature can be represented by different numerical scales (Fahrenheit, Celsius, Kelvin) that capture the same underlying reality, degrees of belief can be represented by probabilities, odds, or other monotonic transformations. Against Zynda and Meacham/Weisberg's challenges, Easwaran defends “strong realism”—for some subjects, degrees of belief can be real features that numbers represent, not mere constructions from preferences. Against Harman and Holton's computational objections, he argues the unconscious mind likely has vast capacity, citing evidence from implicit cognition and skill acquisition. On imprecision, Easwaran suggests apparent indeterminacy often reflects fluctuation over time rather than fundamental vagueness. The chapter establishes that numerical Bayesianism requires no more psychological commitments than other quantitative mental states we routinely accept.