Simplicius on Tekmeriodic Proofs Orna Harari The Department of Classics, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel article info Article history: Received 30 October 2011 Received in revised form 26 December 2011 Available online 28 January 2012 Keywords: Tekmeriodic proofs Autonomy of natural philosophy Simplicius Philoponus Alexander of Aphrodisias Themistius abstract In this study I examine the sole detailed evidence we have for Simplicius’ view of sign-based, i.e. tekme- riodic proofs, thereby questing the widespread assumption that he espouses Philoponus’ account of these proofs. Specifically, I argue that (1) it is more plausible to understand the signs on which Simplicius bases his tekmeriodic proofs as refutable, (2) he grounds the epistemic worth of these proofs in the evidential strength of their premises rather than in their validity, (3) unlike Philoponus, he conceives of the argu- ment that leads to the principles of natural philosophy, which tekmeriodic proofs are aimed to prove, as inductive, and (4) he evaluates these proofs against Plato’s un-hypothetical science, hence denying natural philosophy the autonomy from metaphysics that Philoponus’ account of tekmeriodic proofs grants. Ó 2012 Elsevier Ltd. All rights reserved. When citing this paper, please use the full journal title Studies in History and Philosophy of Science 1. Introduction The late-antique commentators, Philoponus and Simplicius, read into Aristotle’s theory of knowledge a distinction between two types of proof: demonstrative, which proceeds from causes to effects and tekmeriodic, or sign-based, which proceeds from ef- fects to causes and serves as the means of establishing the princi- ples of natural philosophy. Studies of the latter type of proof focus on Philoponus’ account and interpret Simplicius’ account in its light. This approach led to the conclusion that these commentators share the view that tekmeriodic proofs are necessary and valid inferences from irrefutable signs, which have the status of demon- stration secondary in rank. 1 In this study I question this interpreta- tion. By shifting the focus to Simplicius’ description of tekmeriodic proofs, I argue that his analysis of these proofs differs significantly from Philoponus’. Specifically, I show that (1) it is more plausible to understand Simplicius’ tekmeriodic proofs as based on refutable signs and that (2) unlike Philoponus, who grounds the epistemic worth of these proofs primarily in their validity, Simplicius grounds it in their probative force and therefore refrains from describing them as proceeding from posterior, as Philoponus does. Next I argue that these differences reflect Simplicius’ and Philoponus’ views regarding the acquisition of the principles of natural philosophy and the conception of knowledge against which they evaluate tek- meriodic proofs. I show that (1) Simplicius conceives of the acquisi- tion of the principles as inductive, whereas Philoponus conceives of it as deductive, and that (2) he evaluates tekmeriodic proofs against Plato’s un-hypothetical knowledge or dialectic and not only against Aristotle’s demonstrative or explanatory knowledge, as Philoponus does. As a result, I show further, Simplicius denies natural philoso- phy autonomy from metaphysics, even though its principles can be established by tekmeriodic proofs. To prepare the ground for this examination, I discuss Philoponus’ account of tekmeriodic proofs. 2. Philoponus’ account of tekmeriodic proofs in context In the Posterior Analytics I.13 Aristotle discusses an argument which, like a demonstration, proceeds from true and immediate premises, but differs from it in establishing its conclusion not through the cause but from the more familiar (cmxqilώseqom) of two converting terms; for instance, it establishes that the moon is spherical through its increases rather than the other way round, i.e. that the moon increases through its being spherical (78a26– 78b13). Aristotle calls these arguments syllogism from the fact 0039-3681/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.shpsa.2011.12.032 E-mail address: oharari@post.tau.ac.il 1 Morrison (1997, pp. 8–16). Cf. de Haas (2002, pp. 48–49). Studies in History and Philosophy of Science 43 (2012) 366–375 Contents lists available at SciVerse ScienceDirect Studies in History and Philosophy of Science journal homepage: www.elsevier.com/locate/shpsa