Abstract

In this paper I intend to thoroughly analyse Karl Popper’s relation to metaphysics. I start with his first writings, where he states the differences between science, pseudoscience and metaphysics. I then describe how his thoughts on the subject evolved to culminate in his reflection on metaphysical research programmes and the need for a revival of natural philosophy. A major concern is Popper’s famous testability criterion to set apart science from non-science. I point at the problems of the conception of metaphysics as non-testable theories and, in order to avoid these problems, I propose to retain nothing but the traditional conception of metaphysics as the general theories about the nature of the world. This leads me to the conclusion that science is not only an empirical task but also, and in a very important sense, a speculative one.