Brain in a Vat/Evil Demon Thought Experiment

Issue 1, Volume 17

BREE BOOTH

The following headscratcher has been provided to De Minimis courtesy of the Melbourne University Philosophy Society. It forms part of a presentation that will be given at The Clyde on the 11th of March.

René Descartes posited in the Meditations that he could not be sure that all his thoughts were not being placed into his head by an evil demon, whose sole purpose was to deceive him. Thus, everything he perceived as real might be an elaborate simulation designed to make him think that everything he knew was real, when in reality none of it was. 

Rene Descartes: aggressively French philosopher (Wikimedia Commons)

Descartes said: 

​I shall suppose that some malicious, powerful, cunning demon has done all he can to deceive me… I shall think that the sky, the air, the earth, colours, shapes, sounds and all external things are merely dreams that the demon has contrived as traps for my judgment. 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. I shall stubbornly persist in this train of thought; and even if I can’t learn any truth, I shall at least do what I can do, which is to be on my guard against accepting any falsehoods, so that the deceiver—however powerful and cunning he may be—will be unable to affect me in the slightest.

This thought experiment was given a modern update by Hilary Putnam. His formulation asks us to imagine that one may be just a brain in a vat:

Imagine a mad scientist has taken your brain from your body and placed it in a vat of some kind of life sustaining fluid. Electrodes have been connected to your brain, and these are connected to a computer that generates images and sensations. Since all your information about the world is filtered through the brain, this computer would have the ability to simulate your everyday experience. If this were indeed possible, how could you ever truly prove that the world around you was real, and not just a simulation generated by a computer?

The problem explained

Both Descartes and Putnam are positing the same problem, namely: how do we know that everything we experience is not just some complex simulation? Sounds a lot like The Matrix, right? Well, that’s exactly what it is, minus the aliens/post-apocalyptic vigilante angle. 

It’s not difficult to imagine that any given thing we encounter might not be what we think it is. Imagine you’re a farmer, looking out over a field – in the distance you see a black and white shape and infer that it’s your prized cow. However, it turns out that what you saw was actually a large black and white piece of paper that has been caught in a tree. Hence, your senses are able to deceive you. 

Now take this to the extreme: what if your senses were being fed false information so that what you think you see is in fact not there. How do you know that this is not the case? And is it even a problem?

​Bree Booth is a first year JD student and member of the Melbourne University Philosophy Society.