ABSTRACT
The success of action, guided by the rules thus deduced, is the decisive test of the truth of the proposition from which they are derived. But of course it is not left to the individual person to make the experimental tests himself. There may be, and indeed are and have been, many divergent and even contrasted conceptual worlds expressed in equally disparate systems of propositions or “truths.” The superior truth of European medicine over magical remedies can be similarly demonstrated by the cure or prevention of diseases. Despite the prolonged resistance of the Roman Catholic Church, that very European society that had inherited, and for generations believed in, the Ptolemaic system as true, was convinced that it was false. Yet for the purposes of the Greeks and Romans, of the Arabs and of North Europeans, at least before the Great Navigations, it worked well enough and accounted for practically everything that could be observed with the technical equipment then available.
