An example of a historical scientific idea now recognised as an alternative conception:
"[John Joachim Becher] postulated a 'terra pinguis', that is, a fatty or inflammable earth possessed by all substances which could burn. For this fatty inflammable earth he later derived the term 'phlogiston', from the Greek , 'to set on fire'. Phlogiston was fire itself. It was a definite chemical entity of an earthy nature, dry and adapted to solid combination….It was to him and and his followers the touchstone which explained those great chemical reactions of burning, oxidation, and calcination. The vital process of breathing could likewise be explained by it, for did not the lungs constantly exhale phlogiston as food was consumed during digestion in human and animal bodies? When a substance burned, explained Becher, its phlogiston was given off violently in the form of the flame. Weigh the burned body, he said, and you will find that it has actually lost weight in the process, as phlogiston escaped. To him phlogiston was not merely an idea. It was a chemical substance with a definite colour, odour, and weight."
Bernard Jaffe (1934) Crucibles. The Lives and Achievements of the Great Chemists. Jarrolds Publishers.
