Working with map editors for first-person shooter (FPS) games such as Half-Life 2 latched me on to the idea of the "surface of reality". When playing a FPS game, one is immersed in a certain reality which mimics the real world: the laws of Physics apply in this reality as much as the reality we interact with in our daily lives. But this immersion is only skin-deep because what we see and what we hear are only the surface of that certain reality.
When watching a movie shot in a studio, we never see beyond the surface. The moviemakers make sure that we don’t. They take great care that what we see is just the surface, because beyond that surface there is nothing. Beyond the walls of a cozy bedroom is just the ugly superset of reality which is the studio, with wires hanging everywhere and braces here and lighting props there.
In a FPS game, we can move around in the map, and even bump on the wall and hear the effect of that. When going inside a room, the imagery is so real we can almost touch the light bulb and see the effect of doing that to the shades and shadows in that room. When we go near a wall, we can almost feel its texture. However, it can be that the computer model of that room does not go beyond a wall. If we are able to cheat the game and allow ourselves to go beyond a wall, we will experience a discontinuity because there would be nothing beyond that wall. The experience is like jumping into an abyss, into nothingness.
A child learns early that the opacity of an object such as a box can hide a doll behind it, but that the doll continues to exist even when it is out of view.
An animal can survive being aware only of the surface of reality.
When interacting with reality, we deal with it only on the surface. We don’t need to know what is under a bridge while driving a car on it, as long as we are confident that the bridge remains structurally sound and that the car won’t suddenly fall through. We also don’t need to know how the car itself works or feel how much pressure is in the engine combustion chambers, as long as we know that when we step on the gas pedal the car accelerates at the expected level.
The surface of reality is what our perception deals with whenever we are awake and alert. Our perception is acutely sensitive to the laws of physics: instinctively we take it for granted that an apple can fall from the tree. But until Newton asked the question why an apple should fall at all, as human beings we did not understand what gravity is. Understanding nature affords us the potential to conquer more of reality, but it is not required for us, nor for any animal for that matter, to understand in order to function. A dog can catch a frisbee in flight without first learning the physics of frisbees. Much of our perceptive abilities are prewired in us, and we did not need to learn them.