On Keynes's uncertainty: a tragic rational dilemma

Keynes’s uncertainty is a legacy of Greek tragedy: uncertainty as tragic choice. In general, Keynes’s uncertainty is characterised by three conditions: ignorance, low weight of argument (evidential weight) and incommensurability of probability. It is this third condition that I address in my chapter. The non-comparability and incommensurability of Keynes’s logical probability is intrinsic, due to the nature of the material constituting his probability. In Keynes, the material of probability is – in general, apart from a few specific cases – non-homogeneous, since the reasons, grounds or evidence are heterogeneous and incommensurable. There is no possibility to reduce this heterogeneity characterising the material of Keynes’s probability with the use of a common or homogeneous unit of measure, since no common unit of quantities of probability exists; nor is there any possibility of introducing tacit assumptions of atomicity and independence. I consider Keynes’s uncertainty as an incommensurable magnitude; thus, I view uncertainty from a new perspective.