Within the last fifty years, and especially the last twenty, the belief that nature is all there is (i.e. naturalism) and that everything in the universe can be explained by natural processes, has run up against a serious, and perhaps fatal, difficulty.
The problem is that biologists have come to realize that the fundamental substrate of living things is not matter, as naturalism has always held, but information. Information is contained in codes like the amino acid sequence in proteins or the nucleic acid sequence in DNA and RNA, and the origin of information, especially in the first living cell, is inexplicable in terms of random, unguided, unintelligent natural processes.
This 21 minute video does an excellent job of explaining the problem in terms that are easy to understand and follow. It features a protein chemist (Doug Axe) and a philosopher of science (Stephen Meyer), both of whom have played prominent roles in bringing the significance of biological information in the origin of life to public attention.
Any naturalistic explanation of the origin of life has to show how the enormous improbabilities of evolving just a single protein can be overcome by mindless chance. It's a daunting task. Watch the video to see why: