We all know from experience that there is no unity among the sciences. This is so even in the university, where a great many sciences are brought together in one organization. In spite of this diversity and lack of unity there are certain qualities common to all sciences: materially science consists of knowledge that has been sufficiently founded and methodically acquired and is verifiable, objective, and communicable. Formally, every science must have its own relatively wide field of research and must present its results in a logically satisfying form. Because of these common qualities the idea of the unity of the sciences has persisted throughout the history of philosophy to our own time. The problem has always been to find adequate grounds for this unity.
Text of an inaugural address delivered in the Department of Philosophy, University of Pretoria, on June 9, 1970.