The Metaphysics of Science provides a clear, well-founded conception of modern science, according to which its core consists of particular metaphysical principles. On this view, both the empirical and the theoretical aspects of science are the result of the attempt to apply these metaphysical principles to reality. There is a flexibility in the application of the principles, however, so that, in their scientific guise, they may come to be reformed over time through scientific revolutions. This approach to modern science provides a unified conception of the enterprise, explaining such of its various aspects as the principle of induction, the nature of scientific knowledge and scientific reduction, the fundamental difference between the natural and social sciences, and the role of essentialism with respect to natural kinds. Furthermore, it provides a resolution of the longstanding debate between empiricism and realism. In this regard, and in others, the view of science advanced in this work is not only novel, but constitutes an alternative that is superior to both the empiric-analytic and the sociology of knowledge approaches that are prevalent today.