I have always had a great interest in the philosophy of science. At first this interest led to reflections on the mathematical sciences;l later my focus shifted to the natural sciences;2 during the past twenty years or so my interest has also included the behavioral, social, and historical sciences) From the very start my interest was always combined with a concern for the history of the sciences. In philosophy of science proper, my main interest was not in logical, methodological, or even epistemological issues, although I obviously studied and taught the most important insights proposed in the leading publications in this large field of study. My concern has always been predominantly ontological; and in that area I have approached the relevant issues from a 4 phenomenological perspective. For what follows it is perhaps of some importance to mention here that I came to phenomenology in a rather indirect way, through the philosophy of Nicolai Hartmann. Yet it was mainly the influence of Herman Van Breda and Alphonse De Waelhens which led me directly to Husserl’s phenomenology. At first I fo- cused almost exclusively on Husserl’s phenomenology. Later I moved in the direction of the philosophy of Merleau-Ponty and, 1Cf. Joseph J. Kockelmans, Philosophy of Mathematics in the Middle Ages (in Dutch) (Langemark: Vonksteen, 1953); On the Mode of Being of Mathematical Entities (in Dutch), in Tijdschrift voor Philosophie, 16(1954), pp. 289-33l. 2Joseph J. Kockelmans, On Time and Space.