Creationism is no longer the simple notion it once was taken to be. Its new advocates have become more sophisticated in how they present their views, speaking of "intelligent design" rather than "creation science" and aiming their arguments against the naturalistic philosophical method that underlies science, proposing to replace it with a "theistic science." The creationism-evolution controversy is not just about the status of Darwinian evolution - it is a clash of religious and philosophical worldviews, for a common underlying fear among creationists is that evolution undermines both the basis of morality as they understand it and the possibility of purpose in life. In Tower of Babel, philosopher Robert T. Pennock compares the views of the new creationists with those of the old and reveals the insubstantiality of their arguments. One of Pennock's major innovations is to turn from biological evolution to the less-charged subject of linguistic evolution, which has strong theoretical parallels with biological evolution both in content and in the sort of evidence scientists use to draw conclusions about origins.