Joseph Priestley is often said to have discovered Oxygen, or not due to calling it Dephlogisticated air - depending on one's preference. However, regardless of this, it is often said in popular accounts, such as Wikipedia, that due to his continued use of the theory of Phlogiston, he became isolated from the rest of the academic community and the chemical revolution.

I have read some of the works of Priestley, and the related work on Cavendish - who used the Phlogiston theory up to the late 1700s. It is reported in Wikipedia that in 1787 Cavendish was one of the first people to use the Oxygen theory outside of France. The riot that burned Priestley's house was in 1791, and Priestley moved to America in 1794 as a result of his political disagreements. He rapidly became friends with Franklin (perhaps due to his work on electricity, but I have not read up on that). He became ill in 1801 and died a few years later, and before that was simply hampered by lack of contact with the scientific centers in Europe. On the other hand, he was connected to Franklin.

This does not feel to me as though Priestley became scientifically isolated due specifically a unique (others also defended the theory) tendency to support Phlogiston. And indeed no more isolated than would have been likely due to events in his later life. The isolation, such as it was, seems not to have been long, and not really to have related simply to support of the Phlogiston theory.

Are there more details that can be added to support the suggestion of isolation due to support of the Phlogiston theory?


I mention Cavendish in respect of 1787 being the first used of Lavoisier's theory outside of France. Hence, giving a timeline for the acceptance. Further, having read some of Cavendish's papers of the time, I see that he actually supported the Phlogiston theory over Oxygen - for entirely pragmatic reasons. Cavendish was reclusive, and I do not put him there to counter claims of Priestley isolation - Priestley was well published and otherwise connected. On the other hand Cavendish also was an FRS and did attend dinners regularly, even if he would not look at anyone. So, I would not describe Cavendish as isolated. (Thanks to @Conifold for bringing up this issue).

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – Danu
    Apr 29, 2020 at 6:38

1 Answer 1


In researching this question and discussing with @conifold I came to two conclusions. Firstly, that Priestly was active and interactive in the scientific community almost to the month of his death. Secondly, that there is far less support for the suggestion that it is believed that he was rejected from the scientific community due to the Phlogiston debate than was my original impression based on some popular accounts. There is a great deal of believe that Priestley was wrong, but that is not the question I asked.

Having said that, I do believe that a question should be answered in the spirit in which it was asked (this time by me). So with acknowledgement to @conifold for helpful comments (see the chat) I give the result of my research on the matter.

It has been stated in several popular sources that in his later career, Joseph Priestly became isolated from the orthodox scientific community due to his continued and unpopular support for the Phlogiston theory then eschewed by the community at large.


"However, Priestley's determination to defend phlogiston theory and to reject what would become the chemical revolution eventually left him isolated within the scientific community".

This seems to be a misrepresentation of the situation.

Priestly did not start the theory of phlogiston, he used it. Stahl is usually credited with developing the theory in 1703, but the word had been used in 1606 in more or less the same way. Priestly was born 1733, so by the time he was say, 30, it was like being a follower of Einstein in the 1960s. Stahl was generally recognised as giving a good rational theory of some chemical reactions.

Priestly was not a recluse. He had engaged in the late 1700s in a variety of pamphlet campaigns, some of which were considered rather inflamatory and he spoke out against the reformed church. He was described by his opponents as a conflict between a priestly politician and a political priest.

Lavoisier wrote on oxygen (which he mistakenly named acid maker) in 1775 with his Easter Paper to the French Academy. And then started the anti phlogiston movement by responding to Priestly's complaints that Lavoisier had not acknoweldged Priestly's work in the matter, by claiming that Priestly totally misunderstood the experiments and deserved no credit.

Cavendish in England is said to be the first person to start working with the oxygen theory around 1787, however, his papers on this at this time show a mild favoring of the Phlogiston theory. He also developed a theory that effectively equated Phlogiston with Hydrogen, and did a better job of explaining acid reactions than did Lavoisier.

However, by 1797, Kant reported that the Phlogiston theory had been replaced by the Oxygen theory in a rapid change of opinion within the scientific establishment. In 1797, Priestly wrote Observations on Phlogiston and the decomposition of water - which was effectively an explicit defence of the Phlogiston theory against the Oxygen theory.

In 1800, Priestly, himself, was explicitly identifying Phlogiston with Hydrogen rather than oxygen. This is was not a turn around, as the identification of Phlogiston with negative oxygen, a common notion today, was not inevitable. The core issue was to explain the chemical reactions by combinatorics of elements. The details had been under flux for a couple of centuries and would continue to be so for another century.

In November of 1801, Priestly responded to a paper by Cruickshank regarding the chemistry of carbon monoxide. Priestly supported the Phlogiston theory. However, for 1802 and 1803 he seems to have focused on other scientific work. In Priestly's career, the Phlogiston theory was not everything, he defended it strongly and rationally, and does not seem to ever have been converted to the Lavoisier school. But, he defended it in interaction with, and even with some support from, the scientific community of the time.

Priestly died in early 1804. It is hard to say what would have happened next. He might have become a crank ranting about a discarded theory, or he might have been converted, or he might have continued to be no longer interested enough to continue the debate. But, he died, and there seems to be no period of his life in which the image of Priestly rejected by the orthodox science for his loudly proclaimed views is justified.

  • $\begingroup$ The Britannica claims that Priestley's Doctrine of Phlogiston in 1800 was a pamphlet and that the book was 1803. The copy that I have is 110 pages dated on several pages as 1800, so I am inclined to demur. Any way, shifting the date to 1803 seems only to strengthen the idea that Priestly was still active. That it was a Northumberland Press is presumably a matter of location. $\endgroup$ Apr 30, 2020 at 5:37

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.