Fundamental uncertainty and Keynes' probability theory

Abstract

Within economic system agents daily make decisions. Those decisions are based on their expectations regarding future. Therefore, theoretical assumption about what do rational decision-makers really know about future and could agents make relatively reliable forecasts has colossal importance. Namely this assumption critically determines theoretical modeling of decision-making process. In economic theory we can make distinction between two opposite and irreconcilable standpoints on this issue. According to proponents of the Subjective Probability and the Rational Expectations Hypothesis future can be predicted exactly, that is, agents are able to mathematically calculate future precisely and to express it in terms of numbers. Consistently behavior of individual agent and society in aggregate can be predicted with great precision. On the other hand, Keynes, first economist who made clear distinction between risk and uncertainty, argued that past experiences and statistical analysis of past data were not reliable guide to future and that behavior of individual agents and society in aggregate could not be neither calculated exactly nor precisely predicted. Consequently, theoretical implications regarding decision-making and behavior of aggregate economic system of the two opposite standpoints are completely different.