Theory comparison and choice in chemistry, 1766–1791

Abstract

This is the second of a pair of papers, of which the first showed how each of the main late phlogistic theories effectively reached impasses due to internal problems or included features which made them unacceptable even to other phlogistians. This paper deals with theory comparison and theory change. It gives an unprecedentedly detailed comparison between the available theories in 1790-1791, and shows that this was overwhelmingly in favour of the new chemistry. This time period correlates well with many chemists changing to the new theory. There was a plurality of views held by individuals and there was freedom of individual choice concerning theories, yet there was also a widespread and rational change to the new chemistry.

Priestley’s views on the composition of water and related airs

“…McEvoy (1990, pp. 141-142) supported Priestley's claim that both theories had difficulties, but the major differences between the new chemistry and the many phlogistic theories have been demonstrated (Blumenthal and Ladyman 2017b) as well as in the present paper. Conlin (1996, p. 129) claimed that "historians have generally found Priestley's defence of phlogiston not only to be rational but also to be meritorious in various ways" without giving references.…”

“…The inaccuracies of this are being demonstrated in a separate paper. McEvoy (1990, p. 133) also argued that "the empirical adequacies of the competing theories have been virtually equivalent", but the inaccuracies of this have been demonstrated (Blumenthal and Ladyman 2017b) as well as in the present paper. He did not modify these claims in the light of his (1990, p. 139) admissions that Priestley's (1786, pp.…”

“…However, this effectively came at the price of entering an infertile backwater in which he made no further progress in chemistry. By contrast in the cases of participants in late eighteenth-century chemistry who were centrally concerned with developing a fertile way forward in chemistry, after much work it became apparent that the best way of doing this was by identifying the available coherent theory that was as experimentally-testable as practicable, and this dealt with the issue of the very numerous ways in which theories could be compared (Blumenthal and Ladyman 2017b). All this has general implications for how experiments, apparatus and theories are chosen and defended, for how future directions of research are chosen, and for some of the problems with some stances in the history, philosophy and sociology of science.…”