René Descartes' Cogito is an example of a paradigmatic thought experiment, herald of both subjectivism and new science in Europe's Modern Age, that seems to have escaped the attention of thought experiment philosophers. On deep analysis, the Cogito appears as universal instantiation (or modus ponens with implicit major 'whatever has the property of thinking, exists'). The Cogito has strong rhetorical effects for it narratively generalizes from I to all human kind, and its historical and philosophical success can be explained from its concise enthymematic structure that rings true in many possible senses. We consider it a preeminent example of a thought experiment as it states the power of thinking as its very contents. From Descartes' methodology of doubt we can conclude that, e.g., on a Wittgensteinian interpretation, the Cogito is a logical thought experiment rather than a psychological one.KEYWORDS: René Descartes. Cogito (ergo sum). Thought experiment. Modus ponens. Universal instantiation. Semantics. Doubt. Ludwig Wittgenstein.
DEscArTEs' DoubT ThoughT ExpErimEnTThe famous thought experiment of René Descartes (1596-1650) appears in the beginning of part IV of Discourse de la méthode. It is also known as Descartes' Doubt Thought Experiment, and we quote it here in full from the Gutenberg online English translation by John Veitch (DESCARTES, 1901): […] as I then desired to give my attention solely to the search after truth, […] and that I ought to reject as absolutely false all opinions in regard to which I could suppose the least ground for doubt, in order to ascertain whether after that there remained aught in my belief that was wholly indubitable. Accordingly, seeing that our senses sometimes deceive us, I was willing to suppose that there existed nothing really such as they presented to us [TE 1 ]; and because some men err in reasoning, and fall into paralogisms, even on the simplest matters of geometry, I, convinced that I was as open to error as any other, rejected as false all the reasonings I had hitherto taken 1 This article on René Descartes' Cogito thought experiment is derived from Ch. 6 of Semantics of Thought Experiments (HERTOGH, 2015, p. 199-206). Please, see Acknowledgements.http://dx.doi.org/10.1590/S0101-31732016000300002 2 C. P. Hertogh (e-mail noromyxo2005@gmail.com) studied Philosophy at VU University (BPhil), UvA University, Amsterdam (MPhil), and VUB University, Brussels (PhD Thesis Semantics of Thought Experiments-under review).
10Trans/Form/Ação, Marília, v. 39, n. 3, p. 9-22, Jul./Set., 2016 HERTOGH, C. P. for demonstrations [TE 2 ]; and finally, when I considered that the very same thoughts (presentations) which we experience when awake may also be experienced when we are asleep, while there is at that time not one of them true, I supposed that all the objects (presentations) that had ever entered into my mind when awake, had in them no more truth than the illusions of my dreams. [TE 3 ] But immediately upon this I observed that, whilst I thus wished to think that al...