If mystery is not merely a function of ignorance, or obscurity, then what is it? What does it mean for something to be deeper than we can grasp?

In order to get our heads around that, we need to take a little detour. We need to get some idea of the nature of human knowledge—of how we grasp anything at all.

To help us with this, I'd like to introduce a friend of mine, made famous by the philosopher Ludwig Wittgenstein.

If you've met my friend before, you may have some idea of where I'm headed, but if not, you are in for an interesting experience.

Ask yourself what species this fellow is, and make sure you answer, before reading on.

Have you answered? Good. Now notice which side of the eye you are focussing on, as you look at the drawing. It's probably either slightly to the left of the eye, or slighly to the right and above.

Whichever it is, switch your focus to the other side, and see if you can see a completely different animal, facing in the opposite direction.

Most people see a duck if they focus their gaze to the left of the eye, and a rabbit if they focus to the right and a little above the eye.

The purpose of this exercise (aside from the fact that it's fun) is for you to notice just how actively your mind interprets the world. We're used to thinking that we "just see" (or hear, or smell, or feel) the world around us: that we see a duck or a rabbit or a coffee mug or a house directly.

But that isn't quite how it works. An enormous about of interpretation goes into that "just seeing".

As the sketch above illustrates, we actually percieve by classifying. When you classify the sketch as a duck you actually look at it differently (focusing in a different place) than you do when you classify it as a rabbit.

To underline this, let me tell you about an experiment in perception, conducted in the late forties, by Bruner and Postman.

Bruner and Postman put their subjects in a darkened room, and gave them brief, timed glimpses of playing cards. If the subject could not identify the card, the time was gradually increased until he or she could.

Most of the subjects could identify the cards easily, even on the shortest exposures, and all the subjects succeeded at only slightly longer times.

But then, the experimenters introduced some funny cards: a red six of spades, a black four of hearts, etc.

At first, the subjects would identify these anomalous cards incorrectly, as normal cards. Then, as the viewing time increased, they would become hesitant, and begin to have trouble "seeing" the card.

Some subjects couldn't make out what they looking at, even with forty times the exposure needed for normal cards. Some experienced great distress. One exclaimed, "I can't make the suit out, whatever it is. I don't know what color it is or whether it's a spade or a heart. I'm not even sure what a spade looks like. My God!"

On the other hand, after correctly identifying some funny cards, most of the subjects eventually identified other funny cards without hesitation.

So what was going on?

The answer, as you already experienced with our duck-rabbit friend, is that we percieve the world by catagorizing it. The subjects had categories already for ordinary cards, and so had no problem percieving them. But they had no category for the funny cards.

The result was that they could not percieve them, until they managed to form a category for them. Once they had done that, they had no trouble.

A category is not just a name—it may not even have a name. A category is a complex set of frameworks which guide us in percieving and understanding something. It tells us where to look, what to listen for, how to make sense of what we see or hear or smell, and how it fits in our worldview.

And what does this have to do with mystery?

Stay tuned.