Carl Zimmer 10/10/2012 21:00
Hilary Putnam is not a household name. The Harvard philosopher’s work on the nature of reality, meaning, and language may be required reading in graduate school, but Putnam’s fame hasn’t extended far beyond the academy. But one of Putnam’s thought experiments is familiar to millions of people: what it would be like to be a brain in a vat?
Here’s how Putnam presented the idea in his 1981 book, Reason, Truth, and History:
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 whose brain it is 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 travelling from the computer to the nerve endings.
Philosophers have wondered for thousands of years how we can be sure whether what we’re experiencing is reality or some shadowy deception. Plato imagined people looking at shadows cast by a fire in a cave. Descartes imagined a satanic genius. Starting in the 1960s, philosophers began to muse about what it would be like to be a brain in a vat, with reality supplied by a computer. The story circulated in obscure philosophy journals for over a decade before Putnam laid it out in his book.
To track the rise of the “brain in a vat” story, I turned to the Google Ngram Viewer, a web site that can search for any word or phrase you supply in Google’s digital library of millions of books and magazines. After Putnam published his account, the story exploded, the number of times it appeared rising like a rocket into orbit. Hollywood made billions off the image, by making it the basis of the Matrix movie series.
But there’s something telling and important about the success of the brain in a vat that usually goes unremarked. Putnam’s story became an instant hit because it made sense. To see why this fact matters, imagine if Putnam had suggested you imagine an evil scientist had removed your heart, rather than your brain. He put your heart in a vat, and connected its veins and arteries to a computer, causing you to have the illusion that everything is perfectly normal.
This thought experiment would strike a modern listener as absurd. Of course, given the current state of technology, it’s also absurd to think that a human brain could be kept alive in a vat. And yet the idea that a scientist could create a full-fledged experience for someone in their brain remains plausible. It accords with how we think about the brain. We all know that the brain is where we receive sensations, store memories, experience emotions. We all know that all those sensations, memories, and emotions are encoded in electrical impulses in the brain. If indeed you could keep a brain alive, and if indeed you could supply it with the right electrical impulses, then it makes perfect sense that the person whose brain you had extracted would go on having the same experiences as before.
Read the rest at http://beinghuman.org/article/coolin...inking-machine