Abstract

In the mid‐part of the twentieth century, the union of youthful science and the ancient philosophical dream of metaphysical completion begot a visionary doctrine known as the unity of science (see unity of science). This view of the relationship among scientific theories maintained that any theory aspiring to be truly “scientific” must fit into a hierarchy in which every theory was reducible to the theory immediately below it, save for the foundational theory of physics. Reduction would be accomplished by establishing relations of coextension between the predicates of the reduced theory, T1, and the reducing theory, T2, sufficient to allow the mathematical deduction of the laws of T1 expressed entirely in terms drawn from T2 (see reductionism). The classic example is the reduction of phenomenological to statistical thermodynamics. The example suffers from the apparently serious defects of not meeting the conditions laid down by the unity of science and of being pretty much unique in achieving the degree of approximation to these conditions which it enjoys. It has become clear in the later stages of the century that despite the rich and complex interrelationships that prevail among scientific theories, there is little or no prospect of even roughly fulfilling the dream of the grand unification of all theories into a complete hierarchy of reduction. (One philosopher of science, Ian Hacking, bluntly assesses unity of science to be just another of philosophy's “idle pipedreams.”)