Descartes, René (1596–1650)

DOI: 10.4324/9780415249126-DA026-1
Version: v1,  Published online: 1998
Retrieved April 21, 2021, from

4. Doubt and the quest for certainty

In the Rules for the Direction of the Mind, Rule 2 reads: ‘We should attend only to those objects of which our minds seem capable of having certain and indubitable cognition’. While, as we shall later see, Descartes seemed to relax this demand somewhat in his later writings, the demand for certainty was prominent throughout many of his writings. Historically, this can be seen as a reaction against important sceptical currents in Renaissance thought, the so-called ‘Pyrrhonist Crisis’. In the face of the rapidly expanding boundaries of the European world in the sixteenth century, from new texts to new scientific discoveries to the discoveries of new worlds, contradictions and tensions in the intellectual world abounded, making it more and more attractive to hold, with the classical sceptics, that real knowledge is simply beyond the ability of human beings to acquire (see Scepticism, Renaissance; Pyrrhonism). Against this, Descartes asserted that real, certain knowledge is possible; though his name is associated with scepticism, it is as an opponent and not an advocate.

But though certainty was central to Descartes, the path to certainty begins with doubt. In Meditation I, entitled ‘What can be called into doubt’, Descartes says that ‘I realised that it was necessary, once in the course of my life, to demolish everything completely and start again right from the foundations if I wanted to establish anything at all in the sciences that was stable and likely to last’. Following that, he presents a series of three sceptical arguments designed to eliminate his current beliefs in preparation for replacing them with certainties. The strategy is to undermine the beliefs, not one by one but by undermining ‘the basic principles’ on which they rest. While at least some of these arguments can be found in versions in the Discourse and in other writings by Descartes, they receive their fullest exposition in the Meditations.

The first argument is directed at the naïve belief that everything learned via the senses is worthy of belief. Against this Descartes points out that ‘from time to time I have found that the senses deceive, and it is prudent never to trust completely those who have deceived us even once’. The second, the famous dream argument, is directed against the somewhat less naïve view that the senses are at least worthy of belief when dealing with middle-sized objects in our immediate vicinity: ‘A brilliant piece of reasoning! As if I were not a man who sleeps at night… I plainly see that there are never any sure signs by means of which being awake can be distinguished from being asleep’. But even if I doubt the reliability of what the senses seem to be conveying to me right now, Descartes supposes, the dream argument still leaves open the possibility that there are some general truths, not directly dependent on my present sensations, that I can know. Descartes replies to this with his deceiving God argument.

This complex argument has two horns. Descartes first supposes ‘the long-standing opinion that there is an omnipotent God who made me the kind of creature that I am’. Because God is omnipotent, he might have made me in such a way that I go wrong in even the simplest and most evident beliefs that I have – for example, that 2 + 3 = 5, or that a square has four sides. Though God is thought to be good, the possibility that I am so deeply prone to error seems as consistent with his goodness as the fact that I go wrong even occasionally, at least at this stage of the investigation. But what if there is no God, or what if I arose by ‘fate or chance or a continuous chain of events, or by some other means’? In this case, Descartes argues, the less powerful my original cause, ‘the more likely it is that I am so imperfect as to be deceived all the time’.

With this, the sceptical arguments of Meditation I are complete: ‘I am finally compelled to admit that there is not one of my former beliefs about which a doubt may not properly be raised’. But, Descartes notes, ‘my habitual opinions keep coming back’. It is for that reason that Descartes posits his famous evil genius: ‘I will suppose therefore that not God, who is supremely good and the source of truth, but rather some evil genius of the utmost power and cunning has employed all his energies in order to deceive me’. The evil genius (sometimes translated as the ‘evil demon’) is introduced here not as a separate argument for doubt, but as a device to help prevent the return of the former beliefs called into doubt.

These arguments have a crucial function in Descartes’ project. As he notes in the introductory synopsis of the Meditations, these arguments ‘free us from all our preconceived opinions, and provide the easiest route by which the mind may be led away from the senses’. In this way the sceptical doubt of Meditation I prepares the mind for the certainty to which Descartes aspired. But in the Third Replies, responding to criticisms from Hobbes, Descartes notes two other roles that the sceptical arguments play in his thought. Descartes remarks that they are introduced ‘so that I could reply to them in the subsequent Meditations’. As considered below, the deceiving God argument is answered in Meditations III and IV, and the dream argument is answered in the course of his discussion of sensation in Meditation VI. (Since Descartes, quite rightly, continued to maintain that sensation is not entirely trustworthy as a guide to how things really are, the first sceptical argument is never fully answered, though in Meditation VI he carefully sets out the conditions under which we can trust the senses.) Finally, he notes that the arguments are there as a kind of standard against which he can measure the certainty of his later conclusions: ‘I wanted to show the firmness of the truths which I propounded later on, in the light of the fact that they cannot be shaken by these metaphysical doubts’. In all these ways, Descartes presented himself as addressing the sceptic, and defending a kind of dogmatic philosophy.

Citing this article:
Garber, Daniel. Doubt and the quest for certainty. Descartes, René (1596–1650), 1998, doi:10.4324/9780415249126-DA026-1. Routledge Encyclopedia of Philosophy, Taylor and Francis,
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