Synthese DOI 10.1007/s11229-016-1194-x S.I.: CARTESIAN EPISTEMOLOGY Conceivability, inconceivability and cartesian modal epistemology Pierre Saint-Germier 1 Received: 9 February 2016 / Accepted: 10 August 2016 © Springer Science+Business Media Dordrecht 2016 Abstract In various arguments, Descartes relies on the principles that conceivability implies possibility and that inconceivability implies impossibility. Those principles are in tension with another Cartesian view about the source of modality, i.e. the doc- trine of the free creation of eternal truths. In this paper, I develop a ‘two-modality’ interpretation of the doctrine of eternal truths which resolves the tension and I dis- cuss how the resulting modal epistemology can still be relevant for the contemporary discussion. Keywords Descartes · Modal epistemology · Conceivability · Possibility · Inconceivability · Impossibility · Eternal truths 1 Introduction The principle that whatever is conceivable is also possible has both a long history and an acute topicality. While it has its origins in Medieval philosophy (Boulter 2011), it is still discussed today as a principle of modal epistemology, 1 and constitutes a key premiss in the controversial “zombie” argument in the philosophy of mind (Chalmers 1996). When we think about great philosophers from the early modern period who used this principle, Hume is probably the first to come to mind. In the Treatise, he famously 1 See (Yablo 1993; Chalmers 2002) for two influential discussions and Vaidya (2015) for a recent survey. B Pierre Saint-Germier pierre.saintgermier@free.fr 1 Department of Philosophy, University of Geneva, Rue de Candolle 2, Geneva 1211, Switzerland 123