Science is in the business of explaining things. This is because scientific understanding of the world comes to by way of explanations. Science explains why sugar dissolves in water, why unsuspended objects fall, why the planets move like they do, and so on. Explanation is one of the primary aims of science. An explanation is a set of claims/information about dependence relations that exist between the explanandum and the explanans. There is an obvious sense in which explanations generate scientific knowledge. At the beginning of the nineteenth century, it was discovered that the orbit of Uranus, one of the seven planets known at the time, departed from the orbit as predicted on the basis of Isaac Newton’s theory of universal gravitation and the auxiliary assumption that there were no further planets in the solar system. One possible explanation was, of course, that Newton?s theory is false.