Journal of the History of Philosophy

Marin Mersenne and the Probabilistic Roots of "Mitigated Scepticism" PETER DEAR INTRODUCTION WHII.~. vo~ rHsToR,ar~s of science Marin Mersenne is the great correspondent , the "one man scientific journal," for historians of philosophy hc has appeared as an epistemologist. The two important studies of Mersenne in this latter guise are Robert I.enoble's Mer.wnne ou la nai.~sance du mi'canisme (1943),' and Richard H. Popkin's chapters in his The llistory ~ Scepticsm from Erasmus to Spinoza (revised edition 1979)/ For Lenoble, Mersenne is the prototypical modern scientist, rejecting essentialism and establishing a science based on the mathematical coordination of sense perceptions and operational , quantitative predictions. This new vision of science, says Lcnoble, inwflves a radically new regrounding of knowledge, exemplitied in such works as Que.stions inouyes (1634)? which arc compared to the Discour.w on Method? Popkin's view of Mersenne's epistemology differs little fi'om Lenoble 's, although he connects its genesis more closely with particular cultural and political conditions in France in the 162os. l,enoblc argues that Mersenne, being primarily concerned with refuting naturalistic and magical doctrines, wished to maintain the concept of perfectly regular natural law as a means of retaining the interpretation of Biblical miracles as genuine cases of divine intervention. Since Mersenne (for ' Ro[x:rt 1.enoble, Mer.~enne ou la natxmnce du mi'cant.~me (Paris: .1. Vtin, 1943). ~' Richard l-l. Popkin, The Ilt.~too" o]" Scepttct~m [rom Era.~mu.~ to Spinoza (Berkeley: Univ. of " Calitbrnia Press, 1979), csp. drops. 5-7. Set' also the same author's "Father Merscnne's War against Pyrrhonism.'" Modern Schoolman 34(1956-57): 61-78, tbl a more detailed examination of I~,tersennc's own ,,,,ritings. "~ Maritl Mersc:nne, Que.~tmn., mouye~ ou recreation de~ ~favan.~ (Paris, 16,?,4; tacsimile cal., Stuttgart-Bad (]annstatt: Friedt'ich Frommarm Verlag, ~97'~). Lenoblc, Mer~enne. 337-65. [173] ~74 MARIN MERSENNE whatever reasons) rejected scholastic Aristotelianism, which also involved natural law, he needed a replacement possessing an equally strong emphasis on that notion, and found it in a form of "mechanism" (in Lenoble's usage the term does not necessarily refer to corpuscular mechanism). 5 Popkin, on the other hand, places Mersenne's epistemological views in the context of the contemporary popularity of Pyrrhonist arguments. Pyrrhonism, one of the major ancient sceptical schools, argued against the possibility of any form of knowledge, and could be used to support both arbitrary moral positions and fideism. On both counts Mersenne bracketed it with other deviant philosophical and theological positions, and determined to refute it. Popkin maintains that, unable to destroy the central tenets of Pyrrhonism--those which denied that one could ever know the inner natures of things--Mersenne changed the terms of the argument by coming up with "mitigated scepticism ," a position which accepted the impossibility of knowing essences, but claimed certainty for operative, mathematical knowledge of appearances. 6 Both Lenoble's and Popkin's accounts must in large part be accepted. Each emphasizes the role of contemporary epistemologies and theories of nature as creative spurs: what Mersenne did was to develop an alternative to all of them as a means of refutation. The following pages examine the positive side of Mersenne's epistemological ideas, as opposed to those things against which he reacted. The extent to which Mersenne drew upon existing approaches to epistemological problems will be considered in the context of his education, and with reference to the content of his three earliest extant works. These, the Quaestiones in Genesim (together with the Observationes) of 1623, 7 L'impietO des deistes (1624), 8 and La veritO des sciences (1625), 9 reveal, in their very diversity and apparent diffuseness, the intellectual equipment which their author brought to his lifelong crusade of books. 1. Mersenne entered the Jesuit college of La F16che soon after its founding in 16o4, having already received his elementary grammar training at Le Mans. The Jesuits' policy of admitting poor scholarship pupils thus enabled him, although the son of a laborer, to receive one of the finest educations avail5 Ibid., 157-67 and chap. 3 passim. 6 Popkin, History, 13o-37. 7 Marin Mersenne, Quaestiones in Genesim and...