We are constantly perceiving things. Right now, you are receiving the sensation of specific rays of light hitting your eyes which your brain is interpreting as this article. From this sensory information, you have deduced that the electronic device you are reading this article from is within a material realm separate to yourself, occupying space and time. However, some philosophers have challenged this assumption. As Descartes suggests, it could be argued that, because our perceptions are exactly the same when we are awake as when we are dreaming, that it is possible that we could still be dreaming when we think we are awake. If this was the case, instead of your electronic device existing in an external world, it would be a product of your mind. This is something most people find uncomfortable and counter-intuitive to accept. This article explores this problem (as stated by Descartes) and some possible resolutions (through Locke, Hobbes and Berkeley) but it will ultimately conclude that, while we can be persuaded that we are not dreaming, this does not necessarily mean there is an external world.
Descartes explores the problem in Meditations on First Philosophy as part of his method of doubt (a method of examining knowledge where you doubt everything until you find something you are certain of). He believes that there is no difference between our perceptions when we are awake or when we are asleep: if we were to stand near a fire while we where awake, the sensation of heat and light would be exactly the same as if we were dreaming. We would feel the warmth and possibly the pain of the fire in the exact same way in both scenarios. This would lead to not being able to have a distinction between the sensation of being awake as dreaming. Therefore, if we cannot tell the difference between when we are awake and when we are dreaming, then it is possible that we are now currently asleep. We would not be detecting an external world but instead one produced by the mind.
Locke attempts to deal with this problem in An Essay Concerning Human Understanding by rejecting the idea that the sensations we experience while dreaming are the same as the the ones we perceive while awake. He defends this by using passivity and vivacity. When we are awake, the sensations we experience are more vivacious than when we are dreaming: in the case of the fire, we would not feel the heat of the fire in a dream in the same way as if we were to experience the heat of the fire awake. This is because the heat of the fire when awake would feel more vivacious or real than experiencing the heat of the fire while we were dreaming. The pain would feel stronger. Therefore, we can make a distinction between our sensory experience when awake and when we are dreaming so we can tell currently that we are not dreaming.
However, while the argument can provide evidence that we are currently not dreaming, it cannot disprove it completely. While the majority of the time our dreams do not have the same vivacity as our awake experience, there are some dreams that do. There are dreams where we wake up after them and question whether they were real or not. We have to figure out whether we were genuinely next to a fire or whether it was part of the dream. A common example of this is people feeling like they are falling when in reality they are dreaming. Therefore, it is still possible that we are dreaming, it just happens to be an incredibly vivid dream we are experiencing with the same vivacity as reality. Because of this, Locke’s argument does not completely work in disproving the idea that we are currently perceiving a dream, despite casting it into doubt.
While the argument around vivacity may not sufficiently work, other distinctions can be made between when we are dreaming and reality. For instance, Hobbes argues in Leviathan they can be distinguished from each other through their varying regularity and continuity. When we are awake, there is a set pattern to our perceptual experiences which are governed by rules. Using this set of rules, we can make predictions about our future sensory experiences which are, most of the time, correct. For instance, if I want to put my hand in a fire, then I can predict quite confidently it is going to hurt. If the prediction turns out to be wrong, then often there are explanations to why this is. For instance, I may not get burned by the fire, but this is explainable by the fact my hand was covered in a fire proof glove which is a logical reason provided by the Laws of Nature. However, dreams do not follow this pattern – we can do things like fly which would break the rules of our regular experience. There would also be no rational explanation for this breaking of the rules apart from the conclusion that we were dreaming. Therefore, there is a distinction between when we are awake and when we are dreaming. Hence, we can conclude that we are not currently dreaming.
However, while it is possible to strongly suggest we are not dreaming, it doesn’t necessarily lead to the conclusion that some want to gain from it. The whole question of if we can know whether we are currently dreaming is used as a criticism of assuming that there is an external world. By attempting to defeat this problem, philosophers attempt to maintain the existence of such a world. This doesn’t occur as it is possible to not be dreaming but still be observing a non-material world. For instance, Berkeley argues that we can tell that we are not dreaming by the irregularity of dreams compared to the regularity of when we are awake, but he does not insist on a material world. Instead, what we are perceiving is a mind-dependant world. However, while dreams are produced by our own minds, what we call reality is produced by an intelligent “all-perceiving perceiver”. The regularity of our experience is not due to an external world, but because of the rationale of this perceive who projects this bunch of ideas into our brains. Berkeley’s idealism is most often rejected nowadays due to its inclusion of a God which most people don’t believe in. However, the point still stands that we can accept that we are not dreaming, but this does not necessarily mean there is an external world.
Descartes puts forward the idea that it is possible that there is no external world and we could be dreaming. Locke’s argument of vivacity goes a long way to solving this problem, but it is not strong enough to remove the doubt. Hobbes provides a more persuasive argument of regularity that is more convincing. However, while we have a strong argument to suggest we are not dreaming, this does not necessarily lead to the conclusion that realists are looking for; we cannot conclude there is an external world from demonstrating we are not dreaming.