Words Worth Noting - October 3, 2025

“The period during which light was ‘sometimes a wave and sometimes a particle’ was a period of crisis – a period when something was wrong – and it ended only with the development of wave mechanics and the realization that light was a self-consistent entity different from both waves and particles. In the sciences, therefore, if perceptual switches accompany paradigm changes, we may not expect scientists to attest to these changes directly. Looking at the moon, the convert to Copernicanism does not say, ‘I used to see a planet, but now I see a satellite.’ That locution would imply a sense in which the Ptolemaic system had once been correct. Instead, a convert to the new astronomy says, ‘I once took the moon to be (or saw the moon as) a planet, but I was mistaken.’ That sort of statement does recur in the aftermath of scientific revolutions.”

Thomas S. Kuhn The Structure of Scientific Revolutions: 50th Anniversary Edition