Leibniz’s Models of Rational Decision

Abstract

In his article “The balance of reason” Marcelo Dascal has shown that the metaphor of weighing reasons on the scales of the balance of reason is prominent in Leibniz’s writings (Dascal 2005). In this paper, I shall discuss this metaphor and argue that in his practical rationality Leibniz also applied another relatively unknown heuristic model of decision-making, which is related to his work in the philosophy of nature and the philosophy of mind, and which is applied in situations where the values in question compete with each other. These models are based on estimation rather than calculation. I shall concentrate on these two models, which are common in human practical rationality, and leave out the third and most demanding model, the famous calculemus, where the reasons are analysed thoroughly and the analysis itself acts as a kind of method of decision making. With this method, the opponents can in cases of controversy simply calculate the right answer or the highest probability of success of some proposed course of action.1 It is clear, however, that in all human affairs a complete analysis of all relevant reasons is not possible or is extremely difficult and time consuming. This is why Leibniz developed other, less demanding models of rational decision-making.