The philosophical understanding of science that I shall present in this essay is a product of the confrontation of some of my prejudices, or preconceptions, with contemporary developments in science and in reflective thinking. The preconceptions can be roughly summarized by a label 'scientific humanism", which was handed down to me through the works of Descartes, Leibniz, Kant, Hegel, Marx, and other thinkers in the same tradition. According to this tradition, our species as a rational subject is able to discover objective truth and universal norms, upon which systems of thought and action can be built, so that nature can be conquered, social life rationally restructured, and the human being emancipated from ignorance, superstitions and prejudices, from poverty and scarcity, and from all kinds of domination by irrational traditions and arbitrary authorities. In other words, human history is a progressive process toward emancipation, of which reason — its most sophisticated and effective achievement is scientific knowledge — is the major source and vehicle.