What De Finetti Really Meant When He Said “Probability Does Not Exist”: A comment on Spiegelhalter's interpetation

Abstract

Few sentences in the philosophy of probability have generated more confusion than Bruno de Finetti’s famous claim that “probability does not exist”. The line is routinely interpreted as a denial of probability itself, while de Finetti intended only to reject the idea that probability is an objective property of the world. A recent essay by David Spiegelhalter in Nature has reintroduced this ambiguity through an instrumentalist “as-if” formulation. This short note clarifies the distinction between de Finetti’s anti-metaphysical stance, Spiegelhalter’s pragmatic instrumentalism, and E. T. Jaynes’s conception of probability as a form of epistemic objectivity. Recognising these differences helps avoid persistent misunderstandings about what ‘non-existence’ means in probabilistic contexts.