I think, therefore ... well, therefore I think

"How do we know what we know?"

If you endured a college course in introductory philosophy, you know that this is the basic question tackled by epistemology. René Descartes, the French philosopher, argued that we must not assume the absolute truth of anything that could conceivably be doubted. He worked backward, refusing to concede without proof even the existence of the world about us, until he reached one irrefutable axiom: "I think, therefore I am." From his own existence, he then was able to deduce a number of more complex truths, such as the existence of the world that he perceived by his senses, and, ultimately, even the existence of God himself.

But what if Descartes's basic axiom was itself in error. What if "I think" does not necessarily imply "I am"? And what do we mean when we say "I am"?

John Tierney discusses, in an entertaining and rather witty article in today's New York Times, the ideas of an Oxford professor named Nick Bostrom. Dr. Bostrom asks, what if we don't exist? What if we and our universe are just virtual illusions in someone's computer game? This idea is a thought lots of us probably have had, in one form or another, and maybe tossed around with friends while lying on our backs staring at the stars. But the article works through some interesting consequences that might result.

But first of all, let's note that it's not difficult to conceive of the universe as being a virtual world. Quantum mechanics and particle physics show that the "matter" that seems so solid and enduring to us is only the perceived effect of varying combinations of electromagnetic and other forces. Our body is made of elements and compounds, whose properties and appearance are but the effects of certain specific alignments of atoms. Atoms are composed of protons, electrons and other elementary "particles." But these particles themselves are composed of quarks, which can be conceived of as -- if I correctly recall my science classes -- mere statistical probability waves in time/space. Elementary particles certainly do not resemble ultra-tiny grains of sand.

Nothing in the way that physicists describe "reality" seems any more "real" or "common sense" than the digital configurations coursing through a computer. Like a computer program, the reality we call "the universe" is all about information, not about anything permanent or "solid."

If we ourselves are as ghostly as are the virtual characters in a computer's game program, there's no way we can prove it or disprove it. Dr. Bostrom himself concludes that there's a 20 percent chance we are living in a computer simulation. John Tierney says, giving no reasons, make that at least 50 percent.

Whose computer? Who knows? The Times article is entitled: Our Lives, Controlled From Some Guy's Couch. Maybe our Creator is some nerd with a beer belly, a bored geek who can't find a date?

So viewed, immortality is a cinch. A character in a computer game can be killed and revived as often as the software's rules permit. All the information constituting his existence remains in the computer's memory after his "death." A more interesting question might be, which of us will be granted a second life? If the geek playing the game shares our values, maybe because he created them in us to begin with, the good may indeed inherit the earth. But what if the player instead chooses to resurrect those who lead the most interesting lives? This possibility could have a real impact on how we should spend our 70 or 80 virtual years of existence.

Also, the ancient problem of "why does evil exist" now becomes a no-brainer: violence and death are more fun for any red-blooded game player than are peace and happiness.

Much more interesting to Dr. Bostrom is -- what happens when the characters in the game -- we humans -- realize that they are just characters in a game? Or what if the "guy" playing the game is in fact merely a character in someone else's simulation? Not too hard to imagine. We are reaching the point ourselves where we can make extremely good simulations of reality, to the point where the characters in our games themselves might soon show every external sign of being entities with their own thoughts and feelings. How then will we prove that they are "merely" simulations and in any observable way different from ourselves?

What if we become games players ourselves, and our creations themselves eventually become so sophisticated that they realize they are simulations, and indeed become competent to create their own simulations? What if the effect of such a cascade of simulations -- mirrors within mirrors -- is that the ultimate "computer" -- however conceived -- the computer on which the original game was played, and within which we are all entities generated by subprograms -- exceeds its computing power? Tierney's article in the Times concludes that the world might then end not with a bang -- or a whimper, either -- but with a message on the Prime Designer's computer:

It might be something clunky like “Insufficient Memory to Continue Simulation.” But I like to think it would be simple and familiar: “Game Over.”

I feel dizzy. I think I'll go outside and ride my bike!