The Intelligent Design debate continues, fueled by President Bush's recent comment that "Part of education is to expose people to different schools of thought." The problem is that Intelligent Design theory (or ID for short) is not a scientific theory at all. ID is an attempt to "prove" that God (or, in some versions, space aliens) created human beings, using the fact that we don't yet know everything about the universe. It's a philosophical belief, not a scientific one.

It's depressing that some people feel there is a competition between science and religion. Science is merely a tool like any other; a method of using our intelligence to investigate the world around us. It's not science's fault that Liberals have tried to use it to "prove" that God is non-existent or irrelevant. Of course, it isn't possible to prove such a thing; all a religious person has to ask is, "So who wrote all the laws of Nature that scientists are trying to learn? Who determined the value of Pi, the speed of light or Planck's Constant?"

ID is an attempt to disprove the idea that humans evolved through natural selection, by pointing out the fact that there are questions the current theory of evolution doesn't answer. The general argument is that some things are so complex that they must have been deliberately designed; they cannot have evolved naturally over any length of time. There is no actual proof of external interference, however. ID proponents claim that since evolution by natural selection cannot explain everything, the theory must be invalid or incomplete. While that's certainly possible, it doesn't mean that those things can't possibly be explained by further scientific investigation.

Unfortunately, that's precisely how scientific advancement works -- by finding ways to explain what current theories cannot. Science does not mean pointing out that something is not yet fully understood, and deducing that it must therefore have been authored by an outside agency.

Consider the history of another branch of science. Sir Isaac Newton is most well known for the discovery of the laws of gravity. In 1687, he published Philosophiae Naturalis Principia Mathematica, three books that forever changed the course of science. The first two dealt with the laws of motion and forces, the third with gravity. Falling objects accelerate at a rate of 32 feet per second, every second they fall -- a rock dropped off a tall building will fall 32 feet, then 64, then 96, and so on until stopped by the ground, or an inconvenient passer-by. Newtonian physics seemed to explain everything very well for centuries.

As scientists dug deeper into the limits of the physical universe, cracks began to show at the edges of Newton's laws -- situations were found that the accepted theories couldn't explain. No one could predict the relationship and interactions between matter and energy on the very large and very small scale using only Newtonian physics. Along came Albert Einstein, with a whole new explanation of physical science. Did that mean Newton was wrong? Did gravity suddenly stop working when quantum theory was discovered? Of course not. Under local conditions, Newtonian physics are just as applicable as ever. Force still equals mass times acceleration. He simply didn't cover everything -- a fault of the available technology of his time as much as anything else.

A century or so later, Einsteinian physics also begins to show cracks around the edges. There are some situations in which the known laws of quantum mechanics don't seem to apply. Why does time itself seem to act differently under extreme circumstances, like in the presence of black holes? ID as applied to physics would simply conclude that black holes must be alien artifacts. Suppose a new kind of particle is discovered that travels faster than light, like the tachyon. Would that make Einstein wrong? Would his theories become garbage? Of course not. Einsteinian physics would explain and predict the normal interactions of matter and energy as well as ever. His theories simply couldn't cover everything, again due -- at least in part -- to the limitations of his time and available technology.

Even today, Newtonian physics are more than adequate for most everyday situations. Falling objects still accelerate in Earth's gravity at 32 feet per second per second. You don't need string theory to calculate how long it takes a rock to fall, but the fact that such advanced theories exist does not invalidate previous ones. In fact, more advanced theories could not even exist without the groundwork they provide. And at no point should anyone decide that there are Things We Just Cannot Explain, and stop trying to understand them. The same holds true for evolutionary theory as physics.

The laws governing heredity were first published in 1866 by Gregor Mendel, a monk experimenting with pea plants. Plants, like animals, generally have offspring that almost exactly resemble them. He realised that some traits are inherited, but that some variations of those traits are dominant over others. The dominant characteristic would appear in all the results of cross-breeding with plants that had different traits. Even so, the recessive variations don't disappear -- they can return in later generations, if combined with another plant carrying them, though neither plant currently shows the recessive characteristic. Two brown-eyed parents might have a blue-eyed child, if each parent has a blue-eyed ancestor somewhere in their past. Mendel codified the rules by which farmers and breeders of all sorts of plants and animals had operated for thousands of years, without understanding the science behind them.

Mendel's theories didn't cover everything, however. As exploration of the Earth's past progressed, ancient remains had been found that belonged to no living creatures... but which were similar in many ways. Obviously, there was some relationship between modern and ancient creatures, despite the differences. A link must have existed between animals past and present, with creatures slowly changing over vast amounts of time. Enter Darwin, and the theory of evolution by natural selection. Though the concept dates back to the ancient Greeks, Darwin codified the laws governing evolution as Mendel did the laws of heredity... and Newton and Einstein did for physics. Once again, science evolved from understanding the narrow focus and short term to the broad scope and long term, building on the work that had gone before.

Scientific evaluation of the past shows that as environmental conditions change over the course of millions of years, creatures slowly adapt; those who have a slight advantage live longer or better lives, and have more offspring. Due to natural variation, some of their descendants may be even slightly better able to survive, and so on. Did this invalidate Mendel's theories? Were all horse, cow and dog breeders put out of business? Did children no longer resemble their parents? Of course not. In the short term -- hundreds of years, even thousands -- the theory that inherited characteristics breed true is still solid. Your children will still look very much like you, or your parents. When people buy a dog, they don't need to worry what its descendants will look like in a million years.

Now, more than a hundred years on, there are some questions unanswered by current evolutionary theory. So, does that mean Darwin was wrong -- that nothing evolves? Does that mean we should burn that branch of science, and stop investigating our own past using scientific methods? Should we just mark that blank area on the chalkboard, "God did this part" and move on to something else? That doesn't make any sense. That doesn't agree with humanity's history of using our intelligence to discover how things work. Like physics before the advent of Einstein or Stephen W. Hawking, evolutionary science is in need of more investigation when there are unanswered questions, not less. When unanswered questions arise... that's when science takes the greatest leaps forward.

Today, we have access to tools of which Darwin could not even dream. We understand the workings of chromosomes and DNA, and have mapped the very genes that make us human. Turning our backs on knowledge has never really been an option, and deciding that an outside agency must have created us simply because we don't have a more clear mundane explanation YET is not a step forward.