The 'Instrumental' Reality of Phlogiston

The stability of phlogiston in eighteenth-century French chemistry depended not on its role as a comprehensive theory, but on its operational (instrumental), theoretical, and philosophical (speculative) identities that were forged in different contexts, yet were interwoven to designate a single substance. It was as 'real' as any other chemical substance to the degree that it was obtained through material operations, occupied a place in the theoretical edifice of the affinity table, and was endowed with a corpuscular ontology. Lavoisier labeled it as an 'imaginary' substance because it offered a unique resistance to his vision of the new chemistry based on 'metric' measurements and algebraic representations.