Circumventing Cartesian Circles 1 Lex Newman University of Nebraska, Lincoln Alan Nelson University of California, Irvine The tendency in modern philosophy to contrast the doubtful with the warranted is widely attributed to ~indeed, blamed on! Descartes. He proposed that the Phi- losopher’s knowledge should be utterly indefeasible: “so firm that it is impossible for us ever to have any reason for doubting” ~CSM 2:103, AT 7:144– 45!; 2 “so strong that it can never be shaken” ~CSMK 147, AT 3:65!, not even in the face of the most exaggerated doubts which might be contrived by the sceptic. The audacity of such claims is better appreciated in historical context. Des- cartes’ work comes on the heels of a 16th century revival of Greek scepticism, a revival in which the writings of Pyrrhonian and Academic sceptics, and of Mon- taigne, were prominently featured. 3 Adding to the air of defiance, Descartes be- gins his Meditations by introducing a “greatest hits” from the sceptic’s favorite literature, taking care to include the most hyperbolic of contrivances. In the face of such doubts, he purports to then confront and solve the most intractable of sceptical problems impeding efforts to establish a criterion of truth—the Pyrrho- nian dilemma. In Outlines of Pyrrhonism, Sextus Empiricus explains the dilemma: @I# n order to decide the dispute that has arisen about the criterion, we have need of an agreed-upon criterion by means of which we shall decide it; and in order to have an agreed-upon criterion, it is necessary first to have decided the dispute about the cri- terion. Thus, with the reasoning falling into the circularity mode, finding a criterion becomes aporetic; for we do not allow them to adopt a criterion hypothetically, and if they wish to decide about the criterion by means of a criterion we force them into an infinite regress. ~ II 4! NOÛS 33:3 ~1999! 370–404 © 1999 Blackwell Publishers Inc., 350 Main Street, Malden, MA 02148, USA, and 108 Cowley Road, Oxford OX4 1JF, UK. 370