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By Root 582 0

brings Nagel’s idea home with a bang. Suppose we say, “Well, it’s like being Jonesy, the sonar guy on the U.S. submarine in The Hunt for Red October, head down, looking for blips on the sonar screen and listening for pings.” Wrong. That’s what it would be like to be a human inside the head of a bat, using sonar screens to convert the acoustical data the bat receives into human visual experiences. That’s not the way the bat does it. Other suggestions meet with the same objection. We can’t tell what it is like to be a bat. We know only what it’s like to be us, we know only the nature of our subjective experiences. Other organisms have their own kinds of subjective experiences, and even the most extensive neurological study we could make of them and of their brains won’t capture what it’s like to have those experiences. Neuroscience can only show what goes on in the bat’s brain when it’s having its echolocating experiences. It cannot tell us what having those experiences is like.

Once Nagel has you convinced that no amount of neuroscience can tell you what it’s like to be a bat, it’s a small step to the conclusion that no amount of neuroscience can tell me what it’s like to be you—or tell you what it’s like to be me. Can neuroscience tell you what my experience of red is like? No. The only thing neuroscience can tell you about my experience of red is how the neurons are arranged and how they fire when I look at a stop sign. It can tell you a lot, and someday it will tell you everything about the causes and effects of my experience. What it can’t tell you anything about is what my experience of red is like.

The closest anyone can get to telling what my experience of red is like is to look at the same stop sign. If you do, you will conclude, “His experience of red must be like the experience I am now having.” Neuroscience can’t improve on this method. It can’t tell you what it’s like to have someone’s experience, your own or someone else’s. A Martian reading the complete textbook of finished human neuroscience wouldn’t be clued in to what it’s like to experience red or indeed what it’s like to be one of us. Something about reality—that there is a fact about what it’s like to have experiences like ours—will be missing forever from science. This fact about reality will not be one fixed by physics. Scientism refuted.

Nagel drew a more modest conclusion from the bat problem. He didn’t deny that the mind is the brain. He just concluded that we don’t have the slightest idea of how it could be the brain. Other philosophers have gone much further than Nagel. The German philosopher (and sometime Nazi) Martin Heidegger built a whole metaphysics out of the conviction that physics and the rest of science can’t ever explain the subjectivity of experience. Nagel’s example gets at what Heidegger thought was missing from science. Heidegger went further, however. He argued that subjectivity is the most important fact about us, that science can’t explain it, and that we therefore have to reject science as the correct description of reality. We need to build our picture of reality up from the nature of subjective experience. Heidegger is scientism turned upside down.

So, should scientism worry? Certainly not about Heidegger’s version. Almost everything he wrote is just laughably wrong when it’s intelligible at all. In fact, the blindsight results are enough to give us pause not just about Heidegger, but about the magnitude of the problem that subjective experience presents to scientism. It should also help us see the trick in the argument that science will never be able to explain subjective experience.

Blindsight experiments show that knowing what it’s like to see red, what it’s like to have the subjective experience of red, may be unnecessary for understanding vision. In these experiments, blind subjects and even sighted ones whose visual cortex is disturbed can tell what color something is even when they are not conscious of its color. The experiments show that you can do what vision is supposed to do without subjective experiences. That