And like the mousetrap, they are irreducibly complex - they could not have been created by a series of gradual modifications, because without the entire system in place they would fail to function. He argues that design is recognized when you observe a number of different parts interacting with each other to produce a function that none of the parts alone can produce. While all biochemists agree on the existence of such complex cellular systems, Behe admits that few working scientists are willing to acknowledge the idea of intelligent design. At least part of the answer is they think that intelligent design strongly implies something beyond nature. It has strong theological and philosophical implications, and they're uncomfortable with that for one of two reasons.
Some scientists are frankly hostile to religious ideas and reject it for that reason.
In addition to biochemistry, Behe argues that much of late 20th century science in other disciplines also points to the intelligent design position. Then the motion of the galaxies away from each other was noticed, and that gave rise to the Big Bang theory . . . Many people thought that the Big Bang had strong theological implications and didn't like that. Everything seems to be converging on the idea that something beyond this universe is required for life.