DESCARTES DEMON

First published by Headlong (2013)

In his 1641 book, Meditations on First Philosophy, Rene Descartes starts by considering the nature of reality. How do we know, he asks himself, that the world around us actually exists and is not just a projection of our minds?

We perceive what we believe to be the solid external world around us through our senses of sight, hearing, touch, taste and smell. But how reliable is the information that our senses tell us about the world? Our senses can fool us into believing things to be true that are not true. When we look at an object in the distance, for instance, it is easy to think that that object is something different from what it actually is. Our eyes can lie.

We think that because we feel ourselves to exist in the world that the world around us must exist. Descartes observes that as he is writing, he is sitting by the fire in his dressing gown and this feels very real. At the same, though, he acknowledges that sometimes he has dreamt that he was sitting by the fire in his dressing gown and that this felt very real at the time, but then he woke up and realised that he was in bed. How, he asks, can we be sure that we are not dreaming when we are awake or are awake when we are dreaming? He concludes that there is no reliable way of distinguishing reality from a dream. Indeed, a prisoner who dreams he is free, might prefer to live in his dreams rather than confront the harsh nature of his reality.

How can we establish the true nature of our reality? You could rub your eyes to check if you are awake or dreaming. You could feel your hands and stretch them out. But how do you know if your hands and eyes are real and not just figments of your imagination?

Descartes believes strongly that God exists and he wants to believe that God wouldn’t deceive him about the nature of reality. But, he muses, sometimes, we get things wrong. We believe that the object in the distance is something it isn’t and if God can deceive us about a small thing like that, he could be deceiving us about everything.

Descartes is desperate to work out what he can know for certain about reality. He is searching for some indisputable truths about human existence. The only way to do this, he decides, is to assume that the world around us does not exist in any concrete sense. There is no objective external reality. As Descartes hates the idea that God is anything other than a source of truth and goodness, he imagines instead that some malicious demon has deceived him into thinking that the external world exists when it doesn’t.

‘I shall think that the sky, the air, the earth, the colours, shapes, sounds and all external things are merely dreams that the demon has contrived as traps for my judgement. I shall consider myself as having no hands or eyes, or flesh, or blood or senses, but as having falsely believed that I had all these things.’

By believing this, the demon’s power over him is broken. He is no longer deceived into thinking that false things might be true; that external objective reality exists, when it might not.

Unsurprisingly, Descartes now feels as if he is drowning in a whirlpool. He has nothing to cling onto. There is nothing that he can be certain exists or is true. Everything he sees is a fiction. All his memories are false. Even his own body is a figment of his imagination. How then, he asks, can he know that if he actually exists at all?

He concludes that in order for this question to be asked, there must be something asking the question. There must be be some entity thinking the thoughts that he is thinking. To know that you are thinking, is to know that you are real even if the rest of reality is an illusion: ‘I think, therefore I am’.

This article was originally published by Headlong (2013).