A Brain in a Vat

Sporadically, in pub philosophy discussion, or in the midst of a party talking with people a few joints short of a blackout, you will hear a conversation something like this: 

'You know man, like, how do I know you're real? Like how do I know you have a mind? You could just be made up. All this might be like, not real.'

Followed by, 'I totally get you, like, totally.'

Finished with the obligatory; 'I love you man.'

Now it may seem like irrelevant, pointless drivel that everyone will have forgotten about by the next morning, but it has some important implications.

To illustrate, an American philosopher named Hilary Putnam used the idea of a brain in a vat. Imagine that your brain was removed from your head by evil scientists and placed in a vat of nutrients that keep it alive. Your brain is then hooked up to a super technological scientific computer that, by using electrical impulses, can create illusions in the brain; illusions of trees, sky, emotions, people etc. Your brain and subsequently you is experiencing the trees and the sky, but in actual fact you are merely your brain in a vat of nutrients somewhere out in the 'real' world. Matrix fans will see the similarities.

The conundrum has constrained philosophers for centuries and is the dark, looming shadow that quietly hangs over philosophy, threatening to undermine everything that all great thinkers of human kind have proposed. Plato's theory of rule, Kant's theory of knowledge and even Einstein's E=MC2 would all be tossed to the flames if the brain was indeed proved to be in a vat. 

This consequently means that we don't 'know' anything. We can say 'Yes, the sun will rise tomorrow.' and 'Yes, my shirt is blue.' but it cannot be definite knowledge because of this potential that our world in fact does not exist. What is a shirt in a world that doesn't exist? Nothing. The computer screen in front of you, your eyes that you're reading with, the thoughts that you're thinking, they are all part of the illusion created by the brain in the vat. Hilary Putman proposed his analogy in 1981, but it's essentially an updated version of Rene Descarte's thoughts in his 1641 'Meditations on First Philosophy'.

Instead of evil scientists, Descartes proposed that the 'maker' of experience was a 'malicious demon of the utmost power and cunning' that employed all its energies into deceiving Descartes. He believed in innate knowledge; knowledge already built in when we are born, and he also believed that the knowledge was placed by some divine power, for example God or here, the Devil. He questioned the idea that we should believe anything around us because it could quite easily be created by a demon, intent on deception.

Granted, most philosophers don't believe that we are a brain in a vat. And you probably don't either. But it categorically can't be disproved, it's impossible. Any attempt to would be foolish and futile. Instead, philosophers accept and value the theory as healthy scepticism, questioning other theories of knowledge, such as being based on experience or being innately placed, before they run away with themselves.

Yet, the mere possibility that the brain in a vat could exist, continues to cast a large shadow over the world of philosophy.