Darwin's daring idea

Darwin's idea of the origin of species by natural selection is,just like every important idea in natural science, a daring idea, indicating the dangerous path to the discovery of the origin of species. The danger of this path consists in the fact that it leads into the unknown and that it may lead one astray. It is an empirical idea which meets the demands of science: it is testable and internally and externally consistent with other ideas in natural science. This idea, however, does not include an explanatory principle-it does not provide the possibility of deducing the origin of species from initial conditions by means of a law. Instead it leaves us with a principle that is descriptive, interpretative and comprehensive. We can therefore describe the origin of species, interpret it and understand it, but we cannot explain it. The ability to interpret and understand the origin of species is provided because the idea is an algorithm. We are in a situation that can be compared to the one before Pythagoras' theorem was discovered, when people knew the algorithm for the construction of right-angled triangles, but not the theorem from which these constructions could be deduced. In the same way we know today the algorithm for the origin of species, but we do not know the universal law from which this origin can be deduced. Even if we do not know the universal law of biological evolution, we do know its partial laws and we are thus able to give a partial explanation of evolution.