The Early Enlightenment roots of Keynes’ probability concept

In the brief preface to A Treatise on Probability, Keynes states, ‘It may be perceived that I have been greatly influenced by W. E. Johnson, G. E. Moore and Bertrand Russell, that is, by Cambridge, which, with great debts to the writers of Continental Europe, yet continues in direct succession the English tradition of Locke, Berkeley and Hume, of Mill and Sidgwick’ (J. M. Keynes, 1921, p. v). The authors who have recently stressed the relevance of Keynes ideas on probability have paid special attention to the influence of the former, but not to that of the latter. This article intends to show that the Treatise on Probability is deeply rooted in the history of probabilistic thinking, particularly in the Early Enlightenment (roughly between 1650 and 1750), before mathematicians claimed ownership over the subject. We find that important aspects of Keynes’ notions were already present in Locke and other Early Enlightenment writers, albeit with some note-worthy differences.