I challenge Gareth Eaton’s recent claim that Theodore Richards should be counted
among the discoverers of isotopes. In evaluating Eaton’s claim, I draw on two
influential theories of scientific discovery, one developed by Thomas Kuhn, and one
developed by Augustine Brannigan. I argue that though Richards’ experimental work contributed to the discovery, his work does not warrant attributing the discovery to him. Richards’ reluctance to acknowledge isotopes is well document. Further, the fact that he made no claim to having made the discovery also undermines Eaton’s argument.