The Impact that Ramsey's Overlooking of Keynes's Non Additive, Interval Valued Probability Approach in His Reviews of the a Treatise on Probability Has Had on Philosophers and Economists

Abstract

Ramsey’s failure to grasp the interval valued and non additive nature of Keynesian probability assessments in the A Treatise on Probability has led to the misbelief that Keynes’s approach was an ordinal one. While Keynes’s approach easily handles ordinal probability, the theory of the Treatise on Probability is that of “Approximation,” which is interval valued probability. Ramsey’s reviews, however, have been accepted at face value by philosophically interested readers, who fail to grasp that Ramsey has no idea about the fundamental non additive, sub additive, nature of Keynes’s interval valued probability approach. This leads to some very strange assessments of Keynes’s A Treatise on Probability by philosophers who are reading that book.