The Old Brain-in-the-Vat Trick Again

When atheists and theists argue, sooner or later someone will pull the old brain-in-the-vat trick. Typically, the atheist will criticize the theist for offering unfalsifiable arguments for God and use the brain-in-the-vat as an analogy, saying something like, "If we were all brains in vats (or living in Keanu Reeves's Matrix), we couldn't possibly know it. So it wouldn't matter." How that refutes the theist, I'm not sure, but it's certainly true that any empirical theory that is said to be consistent with any and all conceivable states of affairs is worth little. It tells us nothing if it rules out nothing. But more can be said on the brain/vat matter.

First, in serious discussion no room exists for the arbitrary. An assertion proffered without a smidgen of evidence is inadmissible. As I've said before, "what if ...?" in itself is not an argument. The brain-in-the-vat "challenge" is supposed to introduce doubt about what we have no reason to doubt: namely, that we are what we experience ourselves to be -- conscious persons who act in a world that is not a product of our imaginations. As Wittgenstein said about such challenges, "What we can ask is whether it can make sense to doubt.... Grounds for doubt are lacking! Everything speaks in its favor, nothing against it."

Second, Daniel Dennett shows at the beginning of Consciousness Explained (a book I have problems with) that a mad scientist's task of making a brain in a vat believe it is a thinking person who acts in the real world would be so complicated as to be impossible. To use Kant's distinction, the scenario may not be logically impossible, but it certainly would be materially impossible. (As we'll see, even this gives the scenario too much credit.)

Finally, we can go deeper and turn for guidance to J. L. Austin, the great British linguistic philosopher. The brain/vat scenario clearly stands or falls with the philosophical theory that what we perceive are not entities in the world but rather "sense-data," or "perceptions," internally. Somehow, then, the mad scientist is able to feed sense-data to a brain, fooling it into believing it sees, hears, etc. things out there. This theory is intended to introduce doubt about the reliability of our senses -- after all, if something stands between us and things in the world, how can we know that we correctly sort out the "sense-data"? Maybe it's all just a creation of our brains? 

In his lecture series published under the title Sense and Sensibilia, Austin showed the linguistic and other confusion behind this notion. It makes no sense to say that we perceive sense-data and then infer (perhaps wrongly) the existence of things out there. If anything, the story is the other way around. We grow up seeing, hearing, touching, tasting, and smelling things -- and only later on may we contemplate how our sense organs work. Occam's Razor would seem to rule the sense-data theory out of court, but that does not do justice to Austin's case. The "plain man," he says, manages to navigate the world reasonably well -- he's not constantly tripping over things-in-themselves that he misperceived because his senses fooled him. So when philosophers suggest he is naive about perception, maybe it's not the plain man we should question. Maybe the plain man knows what he's talking about when he says he sees not sense data but the cat on the mat. But what about dreams, mirages, and optical illusions, the existence of which are undeniable? The answer is: you couldn't grasp the concepts dream, mirage, or optical illusion without first having experienced reality. No child is flummoxed for long on first seeing a straight stick partly submerged in water; he certainly does not say to himself, "I guess I can't trust my eyes anymore."

I'll provide just a taste of Austin:

Philosophers, it is said, 'are not, for the most part, prepared to admit that such objects as pens or cigarettes are ever directly perceived'. Now of course what brings us up short here is the word 'directly' -- a great favourite among philosophers, but actually one of the less conspicuous snakes in the linguistic grass. We have here, in fact, a typical case of a word, which already has a special use, being gradually stretched, without caution or definition or any limit, until it becomes, first perhaps obscurely metaphorical, but ultimately meaningless. One can't abuse ordinary language without paying for it.

Another way to approach the issue is this: all theories that posit our inability to perceive the world directly sit on the absurd premise that because we have a sensory system, we do not directly perceive the world. In other words, to be direct (veridical), perception would have to be accomplished by no method whatever. But that's ridiculous. All things and their processes have specific natures (A is A and not non-A), so perception too must have a specific means, involving organs, etc. "True" perception cannot be ruled out because we have a method. Ayn Rand did an especially good job of demolishing this view. In criticizing the Kantian position (or at least an interpretation of it) that we don't perceive things-in-themselves, she wrote that in other words, "man is blind, because he has eyes—deaf, because he has ears—deluded, because he has a mind—and the things he perceives do not exist, because he perceives them."

Note further the contradiction in any theory that holds we cannot perceive things-in themselves: it insists that things-in-themselves differ from things-as perceived. But to say that, wouldn't one would have to be able to perceive things-in-themselves? 

The upshot is that since sense-data are the philosopher's concoction, the brain/vat case is nothing more than a science-fiction writer's (rather bad) plot device. We see, hear, etc. the world, full stop. (UPDATE: Which is not to say we don't make infallible judgments about what we perceive. But we correct errors by, among other things, further perceptual investigation.) The mad scientist would be on a fool's errand. 

Now let's hear no more about brains in vats.