“Imagine that a human being has been subjected to an operation by an evil scientist. The person’s brain has been removed from the body and placed in a vat of nutrients which keeps the brain alive. The nerve endings have been connected to a super-scientific computer which causes the person to have the illusion that everything is perfectly normal. There seem to be people, objects, the sky, etc.; but really all the person is experiencing is the result of electronic impulses traveling from the computer to the nerve endings.”
A nightmare scenario, the stuff of science-fiction? Perhaps, but of course that’s exactly what you would say if you were a brain in a vat! Your brain may be in a vat rather than a skull, but your every experience is exactly as it would have been if you were living as a real body in a real world. The world around you—your chair, the book in your hands, your hands themselves—are all part of the illusion, thoughts and sensations fed into your disembodied brain by the scientist’s super-powerful computer.
You probably don’t believe you are a brain floating in a vat. Most philosophers probably don’t believe they’re brains in vats. But you don’t have to believe it, you only have to admit you can’t be certain that you’re not. The problem is that, if you do happen to be a brain in a vat (and you just can’t rule out the possibility), all the things you think you know about the world will be false. And if that’s possible you don’t really know anything at all. The mere possibility appears to undermine our claims to knowledge about the external world. So is there any escape from the vat?
Ideas such as the brain in a vat have proved so thought-provoking and suggestive that they have led to numerous popular incarnations. One of the most successful was the 1999 movie The Matrix, in which computer hacker Neo (played by Keanu Reeves) discovers that the world of 1999 America is in fact a virtual simulation created by a malign cyber-intelligence and that he and other humans are kept within fluid-filled pods, wired up to a vast computer. The film presents a dramatic elaboration of the brain-in-a-vat scenario, all the main elements of which are reproduced. The success and impact of The Matrix is a reminder of the force of extreme skeptical arguments.
Vat origins The classic modern telling of the brain-in-a-vat story above was given by the American philosopher Hilary Putnam in his 1981 book Reason, Truth, and History, but the germ of the idea has a much longer history. Putnam’s thought experiment is essentially an updated version of a 17th-century horror story—the evil demon (malin génie) conjured up by the French philosopher René Descartes in his 1641 Meditations on First Philosophy.
Descartes’s aim was to reconstruct the edifice of human knowledge on unshakeable foundations, for which he adopted his “method of doubt,”—he discarded any beliefs susceptible to the slightest degree of uncertainty. After pointing out the unreliability of our senses and the confusion created by dreams, Descartes pushed his method of doubt to the limit:
“I shall suppose … that some malicious demon of the utmost power and cunning has employed all his energies in order to deceive me. I shall think that the sky, the air, the earth, colors, shapes, sounds and all external things are merely the delusions of dreams which he has devised to ensnare my judgment.”
Amongst the debris of his former beliefs and opinions, Descartes espies a single speck of certainty—the cogito—on the (apparently) sure foundation of which he begins his task of reconstruction (see Cogito ergo sum).
Unfortunately for Putnam and Descartes, although both are playing devil’s advocate—adopting skeptical positions in order to confound skepticism—many philosophers have been more impressed by their skill in setting the skeptical trap than by their subsequent attempts to extricate themselves from it. Appealing to his own causal theory of meaning, Putnam attempts to show that the brain-in-a-vat scenario is incoherent, but at most he appears to show that a brain in a vat could not in fact express the thought that it was a brain in a vat. In effect, he demonstrates that the state of being an envatted brain is invisible and indescribable from within, but it is unclear that this semantic victory (if such it is) goes far to address the problem in relation to knowledge.
Ordinary people may be tempted to dismiss the skeptic’s nightmarish conclusions, but we should not be too hasty. Indeed, an ingenious argument recently devised by the philosopher Nick Bostrom suggests that it is highly probable that we are already living in a computer simulation! Just consider …
In the future it is likely that our civilization will reach a level of technology such that it can create incredibly sophisticated computer simulations of human minds and of worlds for those minds to inhabit. Relatively tiny resources will be needed to sustain such simulated worlds—a single laptop of the future could be home to thousands or millions of simulated minds—so in all probability simulated minds will vastly outnumber biological ones. The experiences of both biological and simulated minds will be indistinguishable and both will of course think that they are not simulated, but the latter (who will make up the vast majority of minds) will in fact be mistaken. We naturally couch this argument in terms of hypotheticals about the future, but who is to say that this “future” hasn’t already happened—that such computer expertise has not already been attained and such minds already simulated? We of course suppose that we are not computer-simulated minds living in a simulated world, but that may be a tribute to the quality of the programming. Following the logic of Bostrom’s argument, it is very likely that our supposition is wrong!
“The computer is so clever that it can even seem to the victim that he is sitting and reading these very words about the amusing but quite absurd supposition that there is an evil scientist who removes people’s brains from their bodies and places them in a vat of nutrients.”
Hilary Putnam, 1981
Skepticism The term “skeptic” is commonly applied to people who are inclined to doubt accepted beliefs or who habitually mistrust people or ideas in general. In this sense skepticism can be characterized as a healthy and open-minded tendency to test and probe popularly held beliefs. Such a state of mind is usually a useful safeguard against credulity but may sometimes tip over into a tendency to doubt everything, regardless of the justification for doing so. But whether good or bad, being skeptical in this popular sense is quite different from its philosophical usage.
The philosophical skeptic doesn’t claim that we know nothing—not least because to do so would be obviously self-defeating (one thing we could not know is that we know nothing). Rather, the skeptic’s position is to challenge our right to make claims to knowledge. We think we know lots of things, but how can we defend those claims? What grounds can we produce to justify any particular claim to knowledge? Our supposed knowledge of the world is based on perceptions gained via our senses, usually mediated by our use of reason. But are not such perceptions always open to error? Can we ever be sure we’re not hallucinating or dreaming, or that our memory isn’t playing tricks? If the experience of dreaming is indistinguishable from our waking experience, we can never be certain that something we think to be the case is in fact the case—that what we take to be true is in fact true. Such concerns, taken to an extreme, lead to evil demons and brains in vats …
Epistemology is the area of philosophy concerned with knowledge: determining what we know and how we know it and identifying the conditions to be met for something to count as knowledge. Conceived as such, it can be seen as a response to the skeptic’s challenge; its history as a series of attempts to defeat skepticism. Many feel that subsequent philosophers have been no more successful than Descartes in vanquishing skepticism. The concern that in the end there is no sure escape from the vat continues to cast a deep shadow over philosophy.
the condensed idea
Are you an envatted brain?
| Timeline | |
|---|---|
| c.375BC | Plato’s cave |
| AD1637 | The mind-body problem |
| 1644 | Cogito ergo sum |
| 1655 | The ship of Theseus |
| 1690 | The veil of perception |
| 1974 | The experience machine |
| 1981 | The brain in a vat |