 Turning Brunetière’s argument on its head, Richet formulated what might be called an ‘optimistic induction’ based on the then recent history of scientific successes. To those who claim that science has failed in the past, his reply is that history shows that it is unreasonable to claim for any scientific question that we will always fail to answer it. Far from warranting epistemic pessimism, the history of science is a source of cognitive optimism. Richet referred to a few remarkable cases, the most striking of which is the case of Jean Louis Prevost and Jean Baptiste Dumas, who had written in 1823: