If a theory claims to be able to explain some phenomenon, but does not generate even an attempt at an explanation, then it should be banished. - Michael Behe

Many people, including many important and well-respected scientists, just don’t want there to be anything beyond nature. They don’t want a supernatural being to affect nature.

... I have no reason to doubt that the universe is the billions of years old that physicists say it is. Further, I find the idea of common descent (that all organisms share a common ancestor) fairly convincing, and have no reason to doubt it. ... I think that evolutionary biologists have contributed enormously to our understanding of the world. Although Darwin's mechanism - natural selection working on variation - might explain many things, however, I do not believe it explains molecular life.

As the number of unexplained, irreducibly complex biological systems increases, our confidence that Darwin’s criterion of failure has been met skyrockets toward the maximum that science allows.