Soups and Sparks Revisited: John Eccles' Path from the War on Electrical Transmission to Mental Sparks

In the famous debate whether neurons communicate via chemical mediators or electrical signals, Henry Dale and Otto Loewi mounted powerful evidence on the mediation of nervous activity by chemical transmitters, while John Eccles led the campaign for the electrophysiologists. Eventually, Eccles converted to chemical transmission, when he identified excitatory and inhibitory postsynaptic potentials initiated by the release of chemical neurotransmitters in the synaptic cleft. This well-known episode from the history of neurophysiology counts as a rare instance of philosophy of science advancing scientific research, because the philosopher Karl Popper had encouraged Eccles to theorize an experiment proving the falsity of his own interpretation - according to Popper's philosophy of science progressing by falsification. The paper shows how Eccles' intellectual mobilization was grounded in a series of geographical moves, technological adaptations and re-arrangements of his group. This massive travel of people, ideas, instruments, and techniques mediated between the contradictory views, long before Popper kindled Eccles to reflect about the conflicting paradigms and the new theorizing did hardly change his experimental practice. Popper's immediate effect was a critical and reflexive distance that enabled Eccles to present his evidence more persuasively, as can be shown from archival sources. The exchanges between Eccles and Popper thus shaped the philosophy of falsification to a powerful strategy for writing science.