Philosophy of science flourished in the twentieth century, partly as a result of extraordinary progress in the sciences themselves, but mainly because of the efforts of philosophers who were scientifically knowledgeable and who remained abreast of new scientific achievements. Hans Reichenbach was a pioneer in this philosophical development; he studied physics and mathematics in several of the great German scientific centres and later spent a number of years as a colleague of Einstein in Berlin. Early in his career he followed Kant, but later reacted against his philosophy, arguing that it was inconsistent with twentieth-century physics.
Reichenbach was not only a philosopher of science, but also a scientific philosopher. He insisted that philosophy should adhere to the same standards of precision and rigour as the natural sciences. He unconditionally rejected speculative metaphysics and theology because their claims could not be substantiated either a priori, on the basis of logic and mathematics, or a posteriori, on the basis of sense-experience. In this respect he agreed with the logical positivists of the Vienna Circle, but because of other profound disagreements he was never actually a positivist. He was, instead, the leading member of the group of logical empiricists centred in Berlin.
Although his writings span many subjects Reichenbach is best known for his work in two main areas: induction and probability, and the philosophy of space and time. In the former he developed a theory of probability and induction that contained his answer to Hume’s problem of the justification of induction. Because of his view that all our knowledge of the world is probabilistic, this work had fundamental epistemological significance. In philosophy of physics he offered epoch-making contributions to the foundations of the theory of relativity, undermining space and time as Kantian synthetic a priori categories.
