The human eye has two interesting properties, one the consequence of the other.
Imagine that you were installing solar panels on the roof. The rig is a big frame, and a bunch of 6×6 solar-panel-ettes. On these, one side is flat and polished, and the other side has a long wire coming right out of the center. Skipping the installation instructions, as you do, presents no major difficulty. You put each little panel-ette in so it faces the same direction: the flat polished side goes to the front of the frame, toward the sun, and the dark center-wired part goes to the back.
When it comes to the wires coming out the back, we wire them together left to right, and we use wire-ties to gather them into a single ever-bigger cable, kinda like so:
Sweet, like a charm. But when you hook it up the output power seems low. In a random debugging impulse, you decide to glance at the installation manual. And it shows everything you did, except exactly backwards. The side that faces the sun is the side that has the wires coming out of it. The side that’s hidden to the sun is the flat polished side.
Imagine the sputtering you’ll emit.
What A Horrible Design!
Well, that’s the first interesting property. The wiring in your eye, receptors on one side, wires on the other, is exactly the design you just dissed. The most sensitive parts of the receptors — rods and cones — is the part that faces towards your brain, where, truth to tell, there is no light. The part that faces the light is the part with the wires coming out of it. The wires — nerves — come out the front.
Eh? Come out of the front?? That’s ridiculous! If that were true, looking at your diagram, there’d be a big hole in my vision, the place where that really fat cable runs out into my brain!
A Hole In Your Vision
That’s the second interesting thing. If you have a big fat cable (of nerves) that comes out from the front of the receptors, then there must be a big fat hole where it comes out of the eye and back to the brain. And that would mean that you have a spot somewhere in your visual field where there’s a hole.
I originally was gonna explain the blind spot to you. This article would be approximately 17 pages longer. Instead, I want you to go play here, and when you’re done, come on back. I’m glad I was able to skip that part.
Your Brain Is A Scoundrel
I don’t wish to put too fine a point on it, but your brain lies to you. All the time. About a lot.
We like to think of ourselves as neutral receivers of data from the environment. Thinking that is what mad Tom Kuhn called living in a paradigm. But it just ain’t so. Every thing you perceive, as this example suggests, is already cooked. Processed. Not raw. Fiddled with. Unreliable. In many cases, wildly unreliable.
A Corner Case? An Optical Illusion?
“Sure, sometimes, my perceptions are fooled by clever pixel-manipulators, but they’re generally straight-up, correct, pixelated, and raw.”
No, actually, they’re not. Over the last thirty years, neurologists and biologists have demonstrated time and again just how cooked our experience really is. It’s not just visual. It’s aural, it’s proprioceptive, it’s feel, it’s taste, it’s smell. Most shockingly of all, at least to me, is that the same stricture applies inside the brain. It’s ego, it’s dreams, it’s memory, it’s reasoning, it’s logic. It is everywhere.
I’m willing to prove that the extent of the cooking is tremendous, touching every thread of your experience, but not today.
Today, I want to trick you into asking yourself a question:
If I Don’t Trust My Brain, What Will I Trust?
It’s a silly question, for all practical purposes. It admits of a great many possible answers: read western philosophy for a host of them, from Descartes forward, all written very poorly.
The bottom line here is that we have no choice. Our experience is cooked heavily by complex systems that broadly and systematically compromise its reliability. But, hey, what else can we do?
We Rely On The Unreliable
* If you want a corner case, the corner case is the rough-and-ready reliability of science. I’m just going to say that and leave it there.