Descartes, René (1596–1650)

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

9. The external world and sensation

The argument for the distinction between mind and body in Meditation VI establishes the nature of body as extension, but it does not establish the real existence of the world of bodies outside of the mind. This is the focus of the last series of arguments in the Meditations. The argument begins in Meditation VI with the recognition that I have ‘a passive faculty of sensory perception’, which would be useless unless there was also an ‘active faculty, either in me or in something else’ which produces the ideas of sensation. Descartes has already established in Meditation IV that the mind has only two faculties – a passive faculty of perception, and the active faculty of will. Since it is passive, perception cannot be the source of my ideas of sensation, and since sensations are involuntary, they cannot be the product of my will. So, the ideas of sense must come from somewhere else. God ‘has given me a great propensity to believe that they are produced by corporeal things’, and no means to correct my error if that propensity is deceptive. So, Descartes concluded, God would be a deceiver if my sensory ideas come from anything but from bodies. This argument does not prove that everything we sense about bodies is reliable, but only that ‘they possess all the properties which I clearly and distinctly understand, that is, all those which, viewed in general terms, are comprised within the subject-matter of pure mathematics’. (In the Principles Part II §1 there is also an argument for the existence of the external world, but it is somewhat different.)

The proof of the existence of the external world tells us that, in general, bodies are the causes of our sensations and it tells us, in general, what the nature of body is. But it does not seem to tell us much about what we can (and cannot) learn about specific bodies in the world around us in specific circumstances. These questions are addressed at the end of Meditation VI in a general discussion of the reliability of sensation, the most extensive such discussion in Descartes’ writings. He argues there that the senses are given to me ‘simply to inform the mind of what is beneficial or harmful for the composite of which the mind is a part; and to this extent they are sufficiently clear and distinct’. That is, while they cannot tell me anything about the real nature of things – that is for the intellect or reason to determine – they can inform me about specific features of my environment that relate to maintaining the union of my mind and body. So, for example, when the senses tell us that some particular apples are red and others green, this can give us reliable information that some may be ripe (and thus nutritious) and others not, but it cannot tell us that the one is, in its nature, red, and the other really green. Similarly, when I feel a pain in my toe, this tells me that there is damage to my toe, not that there is something resembling the sensation that is actually in the toe. Even in this, the sensation may be misleading. As Descartes points out, people sometimes feel pain in limbs even after they have been amputated.

Given the nature of the extended body, and the causal process by which pains (and other sensations) are transmitted through the body to the pineal gland, where the non-extended mind is joined to the extended body, such misleading sensations are inevitable; similar sensations in the mind can be the result of very different causal processes in the body. For example, a sensation of pain-in-the-toe can be caused either by a change in the state of the toe itself, or by an appropriate stimulation of the nerve connecting the toe to the brain at any point between the two. But, Descartes claims, though sensation is fallible, ‘I know that in matters regarding the well-being of the body, all my senses report the truth much more frequently than not’. Furthermore, I can use multiple senses and memory, together with the intellect, ‘which has by now examined all the causes of error’ in order to weigh the evidence of the senses and use it properly. And with this, Descartes is finally able to answer the dream argument of Meditation I. For my waking experience is interconnected in a way in which my dreaming experience is not; the things I see in waking life, unlike those in dreams, come to me through all my senses, and connect with my memory of other objects. I can use this interconnectedness of waking experience, together with my intellect and my knowledge of the causes of error, to sort out veridical sensations and distinguish them from the deceptive sensory experiences of dreams. Sometimes even my waking experiences will be deceptive, of course, but we are capable of determining specific circumstances in which the senses are worthy of our trust. And so, contrary to the original doubts raised by the dreaming argument in Meditation I, there is no general reason to reject waking experience as such.

Though subordinated to reason, sensation, cast into doubt in Meditation I, re- enters as a legitimate source of knowledge about the world by the end of Meditation VI.

Citing this article:
Garber, Daniel. The external world and sensation. Descartes, René (1596–1650), 1998, doi:10.4324/9780415249126-DA026-1. Routledge Encyclopedia of Philosophy, Taylor and Francis,
Copyright © 1998-2021 Routledge.

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