ADVOCATES of intelligent design argue that it deserves to be taken seriously as a rigorous scientific alternative to evolution by natural selection. But just what is it, and is it science at all?

Intelligent design (ID) is more sophisticated than its predecessor, "creation science", which sought to gather scientific evidence in support of the Christian creation story. By starting from a pre-conceived conclusion and selectively using evidence to back it up, creation science was clearly unscientific.

ID is different. Its supporters argue that we can use science to find evidence of a designer's handiwork in nature, while claiming to be agnostic about exactly who the designer is. "Often people think the designer is the Big Guy in the Sky. But it doesn't have to be that at all," says William Dembski, a mathematician, philosopher and leading ID proponent affiliated with the Discovery Institute, a creationist think tank in Seattle. He ...