Modern science began as natural philosophy, an admixture of philosophy and science. It was then killed off by Newton, as a result of his claim to have derived his law of gravitation from the phenomena by induction. But this post-Newtonian conception of science, which holds that theories are accepted on the basis of evidence, is untenable, as the long-standing insolubility of the problem of induction indicates. Persistent acceptance of unified theories only in physics, when endless equally empirically successful disunified rivals are available, means that physics makes a persistent, problematic metaphysical assumption about the universe: that all disunified theories are false. This assumption, precisely because it is problematic, needs to be explicitly articulated within physics, so that it can be critically assessed and, we may hope, improved. The outcome is a new conception of science—aim-oriented empiricism—that puts science and philosophy together again, and amounts to a modern version of natural philosophy. Furthermore, aim-oriented empiricism leads to the solution to the problem of induction. Natural philosophy pursued within the methodological framework of aim-oriented empiricism is shown to meet standards of intellectual rigour that science without metaphysics cannot meet.