Two Republican congressmen are playing fast and loose with accepted definitions by suggesting that their home state should alter its science curriculum to include references to the so-called intelligent-design (ID) theory. Representatives John Boehner and Steve Chabot of Ohio want the curriculum amended to include the language, "Where topics are taught that may generate controversy (such as biological evolution), the curriculum should help students to understand the full range of scientific views that exist."
This might seem unobjectionable, except that most observers agree that the language is being used as a Trojan horse for a theory that is decidedly unscientific. ID argues that the complex nature of life and the universe provide evidence of an organizing intelligence. This is an old notion: The ancients marveled at "the harmony of the spheres," while the early-nineteenth century theologian William Paley likened God to a watchmaker (something as complex as a watch could never have occurred naturally, and so the same must be true of living things).
Intelligent design does have a thing or two going for it. Superficially, at least, it tries to address the concerns of science, being a more sophisticated and less airy attempt than the watchmaker theory at reconciling the human need for divinity with evidence.
ID is not, however, true science. According to the eminent modern philosopher Karl Popper, the defining characteristic of science is that its assertions are falsifiable. In other words, if we have no means to prove a theory wrong -- by experiment, observation, and the like -- then it is not scientific. And theories that cannot be falsified simply have no place in science books or classrooms. (Thankfully, most things to do with nature and the various physical laws can be tested, so our science curricula have plenty of material.)
Some elements of intelligent design can indeed be tested, such as the doctrine of irreducible complexity. This is the contention that complex biological entities cannot have arisen by chance because removing just one element in them often causes them to cease to function. Thus the Catholic biochemist Michael Behe, an ID theorist and author of Darwin's Black Box, has argued that certain biochemical systems within our cells are like a mousetrap: Take away any part of the trap -- the base, the spring -- and it stops catching mice. Therefore, Behe's argument goes, just as a mousetrap was consciously designed (by humans) to trap mice, so these molecular systems must have been designed for the role they play.
This is a false conclusion, however. Most traits of living things that arise by natural selection are advantageous but not essential -- or at least not at first. However, successive traits can then develop that are especially advantageous in combination with a previous trait, in the end making one or both of them essential. An example might be the air-breathing advantage of lungs. At first, this would have benefited an amphibious creature whose habitat was extended by the ability to stray from water onto dry land. But when paired with the extra mobility gained from legs evolved for walking, lungs might have become essential in order to allow the evolving organism to fully thrive in a land habitat. (Another quintessential example, of course, is the eye, an immensely complex organ that nevertheless obviously evolved in stages.)
Intelligent Design theorists such as Behe have attempted to include empirical examples in order to bolster their case. In the end, however, the underlying basis of the theory -- the proposition that a designing intelligence deliberately assembles complex living things -- remains unfalsifiable. We can certainly demonstrate how it is that natural selection can produce very complex organs such as the eye, and thereby falsify one tenet of the theory. But the overarching proposition, of a pre-existing intelligence, cannot be put to any scientific test.
That's why the National Academy of Sciences stated quite categorically that "intelligent design [is] not science because [it is] not testable by the methods of science" in its definitive 1999 investigation, Science and Creationism: A view from the National Academy of Sciences. No amount of dressing the issue up in scientific terms can circumvent this problem. Until the "scientific creationists" come up with a theory that can be submitted, in its entirety, to scientific tests, they must recognize that what they are proposing to teach in schools is religious faith, not science.
And ID fails the test even using an alternative, non-Popperian view of the way the scientific method operates. In his influential book The Structure of Scientific Revolutions, Thomas Kuhn argued that science is ruled by paradigms, worldviews that fit the available knowledge and according to which scientists operate. But intelligent design is not part of any current scientific paradigm, and besides a few fringe elements, no serious evolutionary biologists accept it. Moreover, it is hard to call ID an emerging scientific paradigm when its leading proponent is a University of California, Berkeley law professor, Phillip E. Johnson, who is not a scientist at all.
The only scientific theory of life's origins thus far is the theory of evolution. ID may have a genuine role to play in the classrooms of philosophers or comparative theologians, but it certainly does not belong in the science lab. If creationists want to have their views taught, they must first meet the biggest challenge in history: proving the existence of God.