Descartes Answers: Commentary

This page gives an interpretation of the excerpt from Descartes’ First Meditation.

Descartes presents us with some very simple, yet powerful arguments to begin doubting everything we take for granted. Do we really know that the world is how we think it is? Do we even know that we have arms and legs, heads and chests? Could we not be disembodied ‘minds’ floating around in a different dimension dreaming, or deceived into thinking, that we inhabit a three-dimensional world and live on an imaginary planet we call ‘Earth’? How do we know that this is not the case?

According to Descartes, we cannot trust our senses. We know they can deceive us – just think about how things look larger underwater, or have a different colour under a streetlamp than in daylight; think about mirages in the desert and hallucinations under the influence of tiredness, drugs, or mental illness. In Part I we came across the idea of an argument from authority. One way to understand Descartes’ point here is to say that the senses make claims upon our judgement, but the authority for these claims is not reliable.

Such a view introduces both epistemological foundationalism and ontological dualism, creating what seems to be an unbridgable logical gap between the knower and the source of knowing, which looks at least prima facie justified when the source is external to the subject.

However, just whether our own sensory organs are external to our self raises deep metaphysical questions about the relationship between mind and body: does the self extend beyond my experiences to include the body in which those experiences are had? Descartes’ argument seems to imply that the answer to this question must be ‘no’.

In a wider sense, the kind of argument in which we doubt that something is true is called scepticism, and if it is wholesale scepticism that claims nothing is as we believe, then it is often called radical scepticism.

Alone, the argument from the unreliability of the senses does not do enough to establish radical scepticism. After all, though our senses might be sometimes wrong, we know that they are mostly correct – we know this because the only way we can tell that they sometimes deceive us is by comparing defective perceptions with ordinary sensory experience.

It is for this reason that Descartes introduces the ‘dreaming argument’. The logic here is different. In dreams, things can be wholly unlike the real world, and we have no independent check on whether things that we see in dreams exist or not. More importantly, people can dream that they have woken from a dream, suggesting that being able to tell the difference between a dream and waking reality – at least while we are dreaming – may not always be possible. In that case, doesn’t if follow, at least as a logical possibility, that we could always be dreaming?

Radical scepticism is now not far away, but Descartes sees a flaw in his own arguments. Dreams are, after all, reflections of reality. They do not have an existence of their own. Moreover, if they are reflections of how things really are, then at least their basic elements must be among the things that really exist.

With this in mind, Descartes’ blocks this kind of reply by introducing a third argument, often popularly referred to as the ‘malignant demon’ argument. According to this idea, God could be deceiving us about everything, even the elements of our dreams and mathematics. It could all be a fiction made up in God’s mind, and not be a reflection of reality at all. Perhaps two plus two really equals five, but God just makes us miscalculate every time we do the sum. You do not have to believe in God or demons to buy into this scenario; there are materialistic, atheistic versions such as that which underpins the Matrix trilogy of films and Robert Nozick’s ‘brain-in-a-vat’ thought experiment. God, computers or evil scientists: any one of them could be deceiving us. The question is, could they do it and would we ever know?

Descartes’ answer, ultimately, is ‘NO’ to the first question and ‘YES’ to the second, but you will have to read the rest of his Meditations to find out why. 🙂

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