ID starts with a probability claim. The chances that things would have turned out the way they did are infinitesimally small. Numerous features of the natural world can only properly be explained by the existence of an intelligent designer; it is simply too improbable to be explained any other way. Evolutionary theory, by contrast, posits explanations that are internal to the world it is explaining: it relies wholly on natural explanations.
Because ID uses technical tools such as probability theory, and attends to the biological and palaeontological details, it claims more respectability than creationism. Recently, President Bush endorsed the teaching of ID.
In November, voters in Kansas endorsed an amendment to the state science standards, requiring teachers in the public (state) schools to explain that evolution is "only a theory, not a fact" and encouraging them to teach ID as an alternative to evolution.
Crucial to the Kansas revisions is a change in the definition of science, so that it no longer restricts itself to natural explanations. Supernatural explanations, in other words, might count as scientific. Teaching the supernatural as science is nonsense. But evolution is, indeed, a theory and not a fact.
There are numerous facts about the natural world and evolution is a theory that explains them pretty well. But, like every other scientific theory, it contains anomalies; there are observations it doesn't explain well. The dispute between gradualists (who see evolution as a slow gradual process) and those who see it proceeding in fits and starts is only the most famous.
So there is a grain of truth in the Kansas edict.
When the main "rival" of evolution was creationism, it was relatively easy to admit the grain of truth without fear of muddying the waters. Evolution is only a theory, but creationism is not even a theory; merely a stipulation of an alternative explanation. People are entitled to hold beliefs that they cannot defend without appeal to faith; but these beliefs do not have the same public standing as those that withstand rational scrutiny.
However, Intelligent Design looks much more like a theory. Its advocates are intellectually dishonest, to be sure - they are funded by political backers who want to press a conservative agenda, and they engage with the anomalies in evolutionary theory only to prove their own theory, rather than having arrived at it through engagement with the anomalies.
Nor are they scientists; the "scholarship" in Intelligent Design is not published in science journals but in publications funded by wealthy donors.
But because ID theory uses complex statistics and probability theory, it has a veneer of seriousness.
Scientists are on the defensive. Whereas the ID-ers are paid to promote ID, serious scientists have day jobs, and engaging with intellectual frauds is not part of their job description.
Most people do not have the education or patience to sit through a proper refutation of the ID-ers' claims. And the spirit of relativism haunts the world of public education. A friend, complaining to his child's teacher that she was not teaching evolution, was told: "Children have to decide what their own beliefs are about evolution, and it would be wrong for me to impose my beliefs on them".
The Kansas result is not disastrous. The new standards merely allow room for teaching of supernatural explanations for natural phenomena. There will be increasing pressure to put ID where it belongs, in world religions or philosophy classes. On the day of the Kansas vote, members of an ID-dominated school board in Pennsylvania were swept from office, replaced by opponents of ID.
Defenders of teaching ID are often queasy about having it taught to their own children. Being taught that ID is a serious alternative to evolution not only compromises a child's intellectual development, it jeopardises their prospects of entry to elite colleges that are widely regarded as the key to wealth and success in America.
I doubt that President Bush would impose that risk on his own children; and as the issue gets fought out in the public square, I'd guess most voters will be similarly unwilling.
Harry Brighouse is professor of philosophy and affiliate professor of education policy studies at Wisconsin university