Skepticism, a short uncertain history (5): Descartes’ evil daemon


Together with the discovery of America, the Protestant Reformation was probably the main historical factor in the (European) Modern Age. As we saw in the previous entry, the debate between different Christian denominations was a perfect breeding ground to put into use the recently rediscovered arguments of the ancient Greek Skeptics (though in practice the ‘debate’ was, for 150 years, more the job of weapons and fires), and the main casualty of that polemic was, instead, the Aristotelian, scholastic view of ‘science’ (not distinguishable till then from ‘metaphysics’ or ‘philosophy’) that had developed in the Middle Ages to support the Christian view of the world. Christian faith, however, survived basically intact, though multiply diversified, from these debates of the early Modern Age, with the only caveat that, by the end of the Thirty Years war, it was more or less clear to most ‘intellectuals’ that the dogmas of religion cannot be based at all in ‘reason’, but come from mere faith (though, of course, reason still had an important role in maintaining the internal coherence of the dogmas and to avoid blatant contradictions between them and worldly savoir); but by mid 17th century, (Christian) faith was still seen as a legitimate source of ‘knowledge’, whereas Aristotelian metaphysics had suffered so lethal blows that it had already gone through most of its way to the dusty shelves of the history of philosophy and the obscure aisles of theological faculties, from which he never raised again as a robust foundation of scientific research and knowledge (save, perhaps, in the case of biology, in which it somehow lived a couple of centuries more).

I shall deal in a future entry of the series about the turn from this ‘religion-friendly’ to a more hostile-to-faith species of modern skepticism from mid 17th century on. My topic here will be, instead, the transformation of epistemological scepticism from its more moderate brand prevalent in the Renaissance (i.e., from a version conspicuously addressed towards a limited set of targets), to its most radical version, as a universal claim against basically all forms of knowledge about the world. As it is well known, the author that helped the most to fully open the perilous Pandora’s box of skepticism was René Descartes (1596-1650), mostly in his tremendously influential books Discours de la Méthode (anonymously published in Holland in 1637, though it seems that the author’s identity was soon notorious) and Meditationes de Prima Philosophia (published in Paris four years later). Like the mythological Pandora, Descartes seemed to be confident on his own capacity of closing the dangerous box at his will, but history proved it wasn’t going to be so easy.

After two centuries of, so to say, guerrilla attacks to Aristotelianism (and all the ‘science’ loosely erected in its surroundings) with the help of Pyrrhonian style arguments, Descartes had the idea of mounting something like a global assault, in the form of a more radically skeptical strategy. Instead of making use of a type of argument (or ‘trope’, remember the second entry of the series) here, of another one there, etc., tailored by the knowledge or prejudices of each author to the peculiarities of the thesis or claim he might by trying to refute, Descartes thought that a single strategy could ‘fit all sizes’, and later tradition called this strategy ‘the methodical doubt’: just reject every assertion or hypothesis as if it were totally false, if there is the minimal chance of its not being demonstrated with the most absolute certainty. The French philosopher, as many after him, must have been frightened at the beginning by the destructive power of this argument: what, after all, can be taken as being beyond all possible doubt? Greek skeptics had favoured empirical knowledge above (Platonic-Aristotelian) ‘intellectual apprehension of essences’ in spite of acknowledging the limitation of our capacity of extracting generalities from observations and the multiple sources of error that can affect our senses, but they trusted to some extent immediate experience, what we immediately observe at the commons sense level. Descartes, instead, is the first philosopher arguing that the whole of experience could be a dream or a hallucination, and hence, we cannot assert that we know even what we are actually perceiving; not that we cannot make inferences, generalisations or predictions with the help of it, but that it just can be false that the things we are seen happening right now in front of our eyes are happening.

No better luck enjoyed the ‘truths of reason’, mathematical propositions paradigmatically, what for other schools of thought had been the paramount exemplar of certitude. To show that error can be at the basis of this other ‘source of knowledge’ Descartes invents one of the most wonderful tales of the history of human thought: the ‘evil demon’ (génie malin) that might have created (or been controlling) our brains or minds, so that it makes us experience the feeling of certitude at the moment of considering some false mathematical propositions. I.e., perhaps 2 plus 2 is not equal to 4, but our minds have been maliciously engineered so that we are utterly sure it is. Of course this is a strange hypothesis, but is a conceivable one, since Descartes strategy has been that of rejecting everything that we can conceive to be false, even logic and mathematics fall demolished by the strength of this skeptical argument.

The rest of the story is well known. Descartes found a lifeboat: even if everything I’m thinking is false, it cannot be false that I am thinking it while I am thinking it. Cogito, ergo sum. And, in the same way as Noah repopulated the Earth with the animals saved in his ark, Descartes happily thought he could prove the validity of many areas of knowledge thanks to the primordial certitude he had found. “Everything which I perceived as clearly and distinctly as I perceive the reality of my own mind must be equally true”. Amongst these certain things, Descartes finds the existence of god, by a curious argument: one of the ideas I discover in my mind is the idea of an infinitely perfect being, but, being myself imperfect (for I doubt lots of things and being in doubt is worse than having real knowledge), I cannot be the ultimate cause of that idea of infinite perfection; only an infinitely perfect being can be the creator of the idea of an infinitely perfect being. Hence, that being exists, and is my creator, and has put in my mind the idea of such a being as a kind of ‘logo’ or ‘trademark’, so that I recognise who has been my creator. And if an infinitely benevolent god, instead of an evil demon, has created my mind with all my innate ideas (i.e., those allowing me to discover mathematical propositions), these ideas must also be true. Hence, everything I can discover about the world with the help of mathematics will be absolutely certain. And in conclusion, this (i.e., what we could call ‘theoretical mathematical physics’) is the new kind of science that has to replace the failed, old-fashioned Aristotelian philosophy.

So, skepticism was for Descartes (as for many before and after him) only a moment in the course of a longer philosophical project. But his efforts to close again the cover of his particular Pandora’s box soon encountered many difficulties in the arguments of other philosophers. The génie malin contained in the box had experienced for the first time the joy of open air, and he was not to allow to be caught in his prison again.


Ariew, Roger, 2011. Descartes among the Scholastics. Leiden: Brill.

Moriarty, Michael, 2003. Early Modern French Thought: The Age of Suspicion. Oxford: Oxford University Press.

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