The Theory of Evolution has, since Darwin, been sustained by contributions from many sciences, most especially from molecular biology. Philosophers, like biologists and the man in the street, have accepted the idea that the contemporary form of evolutionary theory has arrived at a convincing and final structure. As it now stands, natural selection is thought to work through the information-handling mechanism of the DNA molecule. Variation in the genome’s constructive message is achieved through random errors of processing called mutations. How that mechanism and its revision works, and how much information it can hold are fundamental questions for the Neo-Darwinian theory to face. It is argued here that neither the operation nor the data content of the genome, as science understand them, can underpin the role Darwinism assigns to natural selection. It follows that we cannot put our confidence in the explanatory force of Darwinian reasoning, but neither is there an alternative to it.