What is the ‘Brain in a Vat’ Argument?

Interested in Philosophy? Read on…

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If you’re reading this, you’re probably interested in a Immerse Education summer school. You’re probably sat at a computer, and your mind will, if you’re anything like me, frequently drift over to kitchen dreaming about your next meal. You’re worried about studying, or work, or a person you think you like. You’re looking forward to the weekend, the holidays, the release of a new film.

What you’re almost certainly not thinking about is whether you’re actually just a brain in a vat. You heard me correctly. Look, I’m not trying to make things difficult for you. If you want to close this tab and move on, go right ahead. Enjoy your Netflix or your Facebook or whatever it is you want to do; don’t mind me.

But just to double check, are you sure you’ll be able to enjoy those things if you’re not 100% on the fact that you’re, you know, a human being that exists in a real world? Netflix has undeniably improved its selection in the last year or so, but even the craziest episode of Narcos is going to fall a bit flat if it turns out the whole world is just a virtual fabrication programmed into your head by scientists in an alternate universe.

Are You Doing the Right Thing?

Philosophy is a real chore sometimes. It can be great fun, teaching us to argue, to recognise our own prejudices, to see the world in a clearer light. But it can still be a bit of a nuisance. I remember how my friends used to react when I told them I was thinking about studying Philosophy at university. They didn’t really see the point: can’t you stop thinking so much and get on with things? How will it help you; don’t you know you’ll never get a decent job? Sometimes I was inclined to sympathise.

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But philosophy appeals to those who have a compulsive drive to think things through. Philosophy insists on making life difficult even for those friends who were so dismissive of it, by posing the rather annoying question of why we should care about getting a decent job, about getting on with things, in the first place.

Reasoning Beyond Perceptions

These are not questions that you only ask yourself once you’ve signed up to an undergraduate course and handed over nine thousand pounds. At some point in your life, possibly soon, possibly many decades from now, you will find the tendrils of doubt creeping into what you previously took for granted. It is not enough to say that you should study management or finance in order to get a good job if you cannot explain what makes a good job good.

It is not enough to say that we should intervene in a Middle Eastern conflict to uphold freedom, if you cannot tell me what ‘freedom’ means or why it matters. It is through philosophy that we set about picking apart our preconceptions and trying to work out what we really think, perhaps even what we ought to think. And whenever we find ourselves critically examining our most fundamental beliefs and behaviours, we are doing philosophy – whether we be inside or outside of the classroom.

Certain great works of philosophy run to the thousands of pages. Kant constructed his Critique of Pure Reason in the concatenated prose of a Prussian genius; modern Continental philosophy is famously verbose. But if you arrive at university to study philosophy, one of the first things you might discuss is a very simple thought experiment that you could perform anywhere, alone, without having read a thing. It is the simple prompt: how do you know that the world outside really exists as it appears to you?

What Are You?

Imagine, we are told, that ‘you’ are not what you see in the mirror. ‘You’ are not your body, and you do not inhabit the room you think you’re in now – not really. In reality, you are no more than a brain in a vat of preserving liquid, stored in a laboratory on the planet Xyz. Scientists at the laboratory have hooked your brain up to dozens of tiny electrodes whose pulses mimic the brain’s communication systems.

They stimulate your brain in certain ways to produce certain perceptions in your consciousness – activating one particular combination of nineteen electrodes, for example, gives you the impression of warmth. Another group of forty-six pulses will make a small wooden chair appear three feet in front of you. And so on.


It’s a completely preposterous scenario. My friends at school would have given up reading long ago in a fit of laughter or a strop of utmost boredom. Of course you’re not a brain in a vat – you’re a human being with a name and a family and a very obvious physical location.

But –

– but isn’t that exactly what you’d say if you were a brain in a vat being perfectly manipulated by scientists? Incredulity is the whole point of the brain-in-a-vat thought experiment. The whole point is that we first react with scorn or annoyance, because it’s so ridiculous – and then we realise that our dismissive attitude has no firm basis. It’s a neat example of the way that philosophy gets us to rethink our beliefs and challenges us to give them a solid justification.

We might respond that it’s just not plausible – that consciousness is not reducible to the electrical fluctuations of a squidgy bit of brain. But even then we have learnt something from our thought experiment, something about the nature of consciousness and its distinctness from questions of human anatomy.

Does it really matter?

We might still respond that the question is a waste of time – we don’t need to bother about being 100% certain that we’re not brains in vats, because the world that appears to us is the world we care about, the world in which all our loves and losses, our achievements and defeats, will unfold. But even then we have made a substantial philosophical judgement in response to the thought experiment that was posed.


Philosophy, after all, is not something restricted to a curriculum at an educational institution. Thinking about life and death, about our choices, about the world that we live in and the words we use to describe it, is doing philosophy. Even the outright rejection of philosophy usually comes backed up by arguments you could call philosophy, if you wanted to be a really difficult person to get on with. We all do philosophy whether we like it or not. My hope is that you will, because there’s an awful lot more to it than brains in vats. But everyone has to start somewhere – even if it is on the planet Xyz.

Interested in the study of fundamental questions about reason and existence?

If you’re intrigued by the above post or if you are keen to learn Philosophy, why not sign up for our award-winning Philosophy Summer School? There you’ll examine how philosophers like Socrates, Nietzsche and others questioned existence and reason.





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