Today I’ll say a little more about the battle between internalists and externalists. When we enjoy sensuous experiences such as sights, sounds, tastes, and tingles, internalism says we are accessing something inside of us. If the mind is in the brain, we’re detecting brain events. Nonsense! says the externalist. We are only conscious of objects out in the world and states of our own bodies. We do not detect our own brain-states.
I realize that there are serious problems with internalism, but it may contain a kernel of truth. Even though experiences seem to present us with external objects, this cannot always be so in any simple way. When we’re dreaming or hallucinating, for example, we are not typically perceiving events in the outside world.
Furthermore, sensory perceptions are actually much less world-like than we may imagine. Perceptions are processed in all sorts of convoluted ways, and the resulting experiences may be quite different from the things we’re perceiving. In fact, systematic visual illusions begin at the point where the surface of the eye meets the air. The air is full of atomic particles, but I visually experience air as if it were nothing. If I perceived air in the same way I perceive walls, I would be as blind as if my head were encased in concrete. It is an enormous distortion of reality to experience air as nothing, and a wall as something, and consciousness involves a great many such useful distortions.
The standard response to problem of illusions and hallucinations is that “we directly perceive external arrangements, but do not always perceive them as they actually are” (Harold I. Brown in Edmond Wright, ed. The Case for Qualia, p. 53). We can’t hear some sounds that dogs can hear, and they can’t see colors as we can. But we’re perceiving the world, and so is Bowser.
“That still smells fishy,” complains the internalist, who maintains, for example, that a pain in your toe is not literally “in” your toe, even though you automatically think of it that way. If sensory inputs stopped registering in your brain, someone could smack one of those little piggies with a hammer and you wouldn’t feel a thing. And if a surgeon stimulated the right spot in your brain, it might seem as if something ghastly was happening to your toe even though no one was touching it.
In one experiment during the 1950s, doctors installed electronic probes in the brain of someone with a severe mental illness. This ethically problematic procedure produced very vivid experiences: “The patient giggles again, transformed from a stone-faced zombie into a little girl with a secret joke. ‘What in the hell are you doing?’ she asks. ‘You must be hitting some goody place.’” In another experiment rats were allowed to press a lever that shot a jolt of electricity into their pleasure centers. They “self-stimulated until they passed out.”
(See http://www.hedweb.com/hedethic/orgasmic.htm.)
Philosophical “innies” also note that if something in the outside world changes, we will only perceive this change if it registers within our minds. But if our way of perceiving the world changes, it will seem as if the world has changed even if it has not. Want to make it seem as if the world in front of you has disappeared? Just close your eyes.
For their ultimate trump card, internalists can whip out the famous brain-in-a-vat scenario: A mad scientist of the future keeps a brain alive in a liquid solution, while stimulating it in a way that triggers seemingly normal sensory experiences. The brain therefore thinks it is inside of a body that’s walking around and living a normal life – the ultimate virtual reality simulation. But it is only in touch with its own internal states.
Some externalists deal with envatment by flatly denying that this brain would experience anything at all, even if its states happened to be identical to, say, the states of your brain right this second. But if a brain in a vat could, in principle, have conscious experiences, this seems to show that internalism is true. Experiential phenomena are, literally, in the head. Does that make sense to you, or do you tend to side with the externalists?
Roger Christan Schriner
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The Mystery of Consciousness, and Why It Matters 