Probability and the conduct of life

Condorcet’s probabilistic approach has also important consequences on a more practi­cal level. In all fields of life where decisions are to be taken, Condorcet stresses, people almost always have to face uncertainty.

in the sciences the aim of which is to teach how to act, as in the conduct of life, man can content himself with higher or lower probabilities, and that... the right method consists less in search­ing rigorously proven truths than in choosing among probable propositions, and above all in knowing how to estimate their degree of probability. (Condorcet 1994a: 544)

In this perspective probability theory is an indispensable tool for estimating in an accu­rate way the data of the problems and the outcomes of alternative choices, and this theory had been developing since the seventeenth century (see Hacking 1975; Daston 1988; Hald 1990). Lively controversies never ceased about the meaning of the main con­cepts of the theory (about mathematical expectation, for example) and their use or abuse in various applied fields, and one prominent critic was d’Alembert himself. In defence of probability theory - and of the use of mathematical expectation - Condorcet developed an important reflection on the nature and significance of its concepts, especially in his 1784-87 “Memoire”, his 1785 Essai and in various other texts and manuscripts, such as Elements du calcul des probabilities. In his view, while the probability of an event is a “purely intellectual consideration” (Condorcet 1994a: 289) that “does not pertain to the real order of things” (ibid.: 291) and does not predict its occurrence - the contrary event can happen - nevertheless “we judge of all the things of life from this probability and it rules our conduct” (ibid.). This probability is the measure of our reason to believe in the occurrence of this event.

It is finally to be noted that Condorcet also calls “probability” the number of votes in favour or against a candidate or a proposal in an election or decision-making process, particularly in his 1785 Essai. While this could seem confusing, it is not in the perspective of voting as judgement aggregation: in absence of any other usable evidence regarding the relevant qualities of two candidates, the number of votes may be taken as the best probabilistic indicator of those qualities.