This week, a federal court in Harrisburg, Pennsylvania, began hearing arguments about whether a school can promote intelligent design in the classroom (see 'School board in court over bid to teach intelligent design'). A lawsuit brought by 11 parents of students in the Dover school district alleges that the local school board is violating the constitutional separation of church and state by requiring a statement promoting intelligent design to be read before teachers begin lessons on evolution.

Over the past few years, many scientists have worked hard to discredit intelligent design — but a favourable court verdict could damage the idea more than any amount of academic condemnation. For intelligent design was itself designed, in large part, to get around earlier court decisions that barred creationism from the classroom.

The first such ruling, by the Supreme Court in 1987, overturned a Louisiana law mandating that ‘creation science’, which sought to verify biblical creation through scientific enquiry, be taught alongside evolution. The second was a 1992 Arkansas finding that its very teaching violated the separation of church and state.

Intelligent design is a vaguer concept than creation science, and deliberately so. It posits only that an intelligent creator shaped the course of evolution. The general idea has been discussed by theologians since Darwin's time, but it was only after these court rulings that it gained a significant following in the United States.

Unlike creation science, intelligent design is not affiliated with any specific religion. Rather than trying to prove its own explanation of the origin of species, it aims to punch holes in scientific doctrine. Its supporters, many of them fundamentalist Christians, have been hoping all along that the concept is sufficiently secular for the courts to permit its teaching in public schools.

If these hopes are realized, and the court rules in favour of the Dover school board, the movement is likely to spread quickly into many school districts. Political support for intelligent design, which has thus far been muted, would probably expand (see Nature 436, 753; 2005).

If the court rules in favour of the Dover school board, “intelligent design” is likely to spread quickly into many school districts.

But if the court rules in favour of the plaintiffs, this will seriously undermine efforts to get intelligent design into the classroom. What's more, Christian fundamentalists — some of whom are put off by intelligent design's ecumenical flavour — might then be inclined to abandon it for old-fashioned creationism.

Scientific organizations are well aware of this case's significance, and many have lent public support to the plaintiffs. A ruling in their favour will be welcomed not just by scientists and teachers but by American parents, whose children need to be protected from an injection of superstition into science teaching.