Abstract

In the nineteen-sixties, plate tectonics became the accepted theoretical framework in the earth sciences. This framework revived the idea of continental drift that had been first proposed in 1912 by Alfred Wegener (1966). This paper offers an analysis of the arguments of Wegener and his opponents. We shall show that from Wegener’s perspective his hypotheses possessed a high degree of explanatory coherence, while from the opponents’ perspective his theory was incoherent with much that was generally known.Our analysis uses a new theory of explanatory coherence that has already been applied to several important cases in the history of science: Lavoisier’s argument for his oxygen theory against the phlogiston theory, Darwin’s argument for the theory of evolution by natural selection, and current disputes about why dinosaurs became extinct (Thagard 1988b). This theory is implemented in a connectionist computer program called ECHO that takes statements of explanatory relations as input and creates a network of units, crudely analogous to neurons, with excitatory and inhibitory links among them.