It Is Impossible to Understand Keynes’s Logical Theory of Probability without An Understanding of Part II of Keynes’s a Treatise on Probability: The McCann-Bateman Exchanges Over Ramsey’s Critique of Keynes of 1992

Abstract

The crucial differences between Keynes’s and Ramsey’s theories of logical and subjective probability are insurmountable Keynes’s theory is based on propositions, imprecise, Inexact, interval valued probability (or decision weights that are non-additive), and deals with degrees of rational belief while Ramsey’s theory is based on actual events or outcomes, is precise and exact, additive, and deals with degrees of belief. The only overlap between the two theories occurs if, and only if, Keynes’s w, 0≤w≤1, which measures the completeness of the evidential weight of the Argument, V(a/h), equals 1 and probability preferences are linear. L J Savage’s important restriction, ignored by most all economists ,that his subjective theory of probability can only be applied to Small worlds (micro and short run) and never to Large worlds (macro and long run), would be a compromise that Keynes would most likely have accepted, since the question of Keynesian weight measured by w, usually does not show up in short run, micro applications, but only in long run, macro and intertemporal applications. However, Ramsey never inserted any such restriction to his theory. The McCann-Bateman exchanges demonstrate that neither McCann nor Bateman understand the great, yawning abyss that separates the precise theory of Ramsey from the imprecise theory of Keynes. There are no extant philosophers or economists, as of 2021, who understand this point, as well as why it was simply impossible for Keynes to have accepted Ramsey’s theory in any way, shape or form or to have ever been the slightest bit worried about the so called “points” Ramsey thought he was making against Keynes’s alleged “non numerical “ probabilities, which Part II of the A Treatise on Probability demonstrate are interval valued.