My Bedroom Fan

I spend a lot of time contemplating the fan that spins over my bed. This is a picture of it. That’s approximately how it looks to me most of the time. But that’s not how it really is. In reality the fan is a hub and spoke system with five blades. But when the blades are spinning, they cannot be discriminated and the fan looks more like a solid wheel.

Why is that? Why can I not see the fan as it really is? Why do I see a false image, of a wheel that is not actually there? Am I hallucinating? No matter how carefully I stare, I cannot see actual fan blades. What am I seeing, if not reality? This should shake my confidence in the veracity of vision. Except for tricks and special situations, we generally believe that “seeing is believing.” In other words, what we see is what is there.

But this is a clear case of seeing what is not there, and not seeing what is there. And it is not a trick or special situation. Apparently, the mechanics of my eye cannot resolve the details of the blades as they spin. In order to fixate an image of something on the retina, the image must be still, for a moment at least, about a fifth of a second. That’s the only way we can see something.

What about things that are moving? We can see those under normal circumstances because the eyes take successive “snapshots” of the scene and integrate them over time to communicate movement to the brain, much as the rapid succession of snapshots in a film appears to us as a moving picture (another delusional visual experience). We do not actually see motion. We infer motion.

But in the case of my fan, the movement of the blades is faster than the snapshot rate of my eyes, so I cannot get a fixed image of the blades. The eyes are always moving, jerking around in a process called the visual nystagmus. They vibrate at least 20 times a second, sometimes faster, fixating here, there, everywhere, taking snapshots. It seems like the visual world is stable and that we just look at it and see it as it is, but that is not true. The eyes get at least 20 snapshots per second, no one of them taking in the whole scene. Each snapshot is with the eyes focused on a restricted detail of the scene. Then you synthesize the overall scene in your brain, based on the snapshots. The nice stable scene you think you see is a total fiction. You never saw it. You only saw dozens and dozens of tiny snapshots.

So I thought I would try to beat the visual system and my bedroom fan. I moved my eyes in a fast counter-clockwise motion around the hub, to see if I could make my eyes catch up with the fan blades. And it worked! Every few seconds, I would get a brief image of the individual blades of the fan. That’s because the muscles and nerves for voluntary eye movements are different from the ones used in the visual nystagmus. By adding the two eye movements together, I gave the nystagmus a chance to make a fixation on the blades.

It seemed to work randomly. Whenever there was an eye fixation that happened to hit a blade and not the space between blades, I would see an individual fan blade. Why this did not occur more often, I am not sure. Perhaps I also needed to catch a moment when the blurred motion signals to my brain were calm enough to let an individually fixated image through. Or perhaps my voluntary, circular eye movements were not really very circular, but most often erratic. It is impossible for me to know that.

Anyway, the demonstration proved visually that the blurred circular image I normally see is a complete illusion, not the reality of what is there. The fact that I could force the visual system to apprehend the true reality of the individual blades confirmed the presence of the illusion. So it makes me wonder, what else am I seeing that is illusory? How can I trust that what I see is really there if I know for a fact that sometimes I am seeing it wrong?

Descartes asked this same question in 1640 and came up with this answer: God is good, and God would not deceive you (most of the time). Therefore, you can be reasonably confident that what you see is what is there. Well, that answer doesn’t work for me. In the first place, it is not entirely clear that God is good. Biblical and contemporary evidence would speak to the contrary.

Secondly, my experience with my bedroom fan proved that Descartes’ answer is wrong in this case. What I see most of the time is clearly illusion. Should I assume that God deceived me because God is a malicious trickster?

And finally, Descartes had no evidence to support his claim. It is merely what he believed, because he had been told as much by the Church. I can’t assume his answer is correct if he just made it up or parroted what he had been told. It seems just as likely that the correct answer is that you cannot and should not believe that what you see is what is there. What’s wrong with that answer?

Outlaw the Magnifying Glass!

How does a magnifying glass magnify? What is its secret? I looked into this recently and was amazed to discover that it works by playing on the human delusion that the world is just as it appears. A magnifying glass leads to a dangerous mind-game!

When you want to look at something very small, you have to move your eye closer to it, but there is a limit to that strategy. You can move a sheet of paper closer to your eyes but at some point it is too close for you to focus the lens of your eye on anything. For ordinary newsprint that distance is about 10 inches for me. Closer than that and the print is just a blur. The lens of the eye has a variable focal length, but it has limits.

Incoming light rays are bent by the lens at the top and the bottom, but pass straight through the middle. That’s how a lens works. The resulting image on the back of the eyeball is upside down, but we are so used to that, we don’t even notice it and we see the world as right-side-up.

To get a better look at a small object, we insert a magnifying lens between the eye and the object.






The magnifying glass is held close to the small object, so in the drawing above, the light rays from the object are diverging outward, so much so that an eyeball placed that close couldn’t bend them down to the scale of the retina (couldn't focus them).

The lens of the magnifying glass bends the rays of light just enough so they fit into the lens of the eye, which can take it from there and focus the object. You can move the magnifying glass back and forth until you find that good distance.

So now your eye can focus the object but why does that make the object seem bigger (magnified?). That’s where the mental delusion comes in. As far as the eye is concerned, if light rays come in at that angle, at that distance, they must be coming from a much larger object. The dashed lines show what the eye “assumes” about those light rays and where they came from.

The eyeball is not very smart and does not understand the optics of a magnifying glass. It only knows, from its whole life of experience, that when light rays come in at that angle, at that distance, the object is large. That is the message it sends back to the brain.

Consequently, when using the magnifying glass, we see the object as much larger than it really is, out of “eyeball habit.” THERE IS NO LARGE OBJECT out there. We see a magnified large object that does not exist! The actual object is the same size it always was. But by tricking the eye, we delude ourselves into seeing an imaginary larger object.

The larger, magnified object is utter fantasy, but we don’t interpret it that way. We implicitly assume that we are looking right at an actual object that just happens to be enlarged. As if objects in the world could really be enlarged on demand!

That’s not how the world works. Things are the size they are. They do not get larger because we wish them to. So why do we accept without worry that we have just magically enlarged an object? A magnifying glass promotes an incredible delusion!

Magnifying glasses should be regulated by the government. We cannot allow children to use magnifying glasses! A magnifying glass is far more dangerous in distorting the mind than any hallucinatory drug.