Leibniz and the Ethics of Probability

Chris Meyns (University College London, University of Toronto), Chris Meyns

Amid the recent interest in Leibniz’s contributions to the theory of probability, studies of his mathematical and logical work (especially in combinatorics) have overshadowed attention to his attitudes to the moral and social dimensions of probability. This is remarkable, given that Leibniz’s statements in this area bring up a tension. On the one hand, in various letters from the 1690s Leibniz expresses a dismissive, skeptical attitude to assessments of probability, as though they could lead to lax morals. At the same time Leibniz sometimes equally identifies the measurement of probabilities as the way forward in deciding moral disputes. So what is his stance? Drawing on evidence from both his early and later works (including De conditionibus (1665), his correspondence with Bernoulli, and response to Locke in the New Essays (1703-5)), here I will argue that the observed tension is merely apparent, and that Leibniz’s approach to the ethics of probability is internally consistent. I bring out how Leibniz responds to two competing theories of probability. Leibniz moves away from a scholastic account on which something counts as ‘probable’ when it is supported by an aggregate of views, and he moves toward an understanding which centers on objective reasons, regardless of whether it is an individual or a group doing the assessing. I demonstrate how this dual orientation shapes Leibniz’s approach to probability as a science in the social and moral domain.