Chemists have made of phlogiston a vague principle which is not at all rigorously defined, and which, in consequence, adapts itself to all explanations in which it is wished it shall enter; sometimes it is free fire, sometimes it is fire combined with the earthy element; sometimes it passes through the pores of vessels, sometimes they are impenetrable to it; it explains both the causticity and non-causticity, transparency and opacity, colours and absence of colours. It is a veritable Proteus which changes its form every instant. It is time to conduct chemistry to a more rigorous mode of reasoning ... to distinguish fact and observation from what is systematic and hypothetical.

Combustible bodies do not reduce the metals by giving them phlogiston, as the Phlogistians suppose; nor buy uniting with, and separating their oxygen, as the Anti-phlogistians maintain.
Rejecting older theories of combustion.

I have witnessed a most remarkable drama here, one which to me as a German was very unexpected, and quite shocking. I saw the famous M. Lavoisier hold a ceremonial auto-da-fe of phlogiston in the Arsenal. His wife... served as the sacrificial priestess, and Stahl appeared as the advocatus diaboli to defend phlogiston. In the end, poor phlogiston was burned on the accusation of oxygen. Do you not think I have made a droll discovery? Everything is literally true. I will not say whether the cause of phlogiston is now irretrievably lost, or what I think about the issue. But I am glad that this spectacle was not presented in my fatherland.

If everything in chemistry is explained in a satisfactory manner without the help of phlogiston, it is by that reason alone infinitely probable that the principle does not exist; that it is a hypothetical body, a gratuitous supposition; indeed, it is in the principles of good logic, not to multiply bodies without necessity.

To Monsieur Lavoisier by appointment. Madame Lavoisier, a lively, sensible, scientific lady, had prepared a dejuné Anglois of tea and coffee, but her conversation on Mr. Kirwan's Essay on Phlogiston, which she is translating from the English, and on other subjects, which a woman of understanding, that works with her husband in his laboratory, knows how to adorn, was the best repast.