In theology, he belonged to an influential group of followers of Edmund Law that included also John Hey and William Paley.He became Professor of Chemistry in 1764 and was elected a fellow of the Royal Society in 1769 after publishing a paper on the solution of salts in Philosophical Transactions.Watson contributed to the Revolution controversy, with A treatise upon the authenticity of the Scriptures, and the truth of the Christian religion (1792) and most notably in 1796 when he delivered his counterblast to Thomas Paine's The Age of Reason in An Apology for the Bible which he had "reason to believe, was of singular service in stopping that torrent of irreligion which had been excited by [Paine's] writings".Gilbert Wakefield, a Unitarian minister who taught at Warrington Academy, responded with A Reply to Some Parts of the Bishop Llandaff's Address to the People of Great Britain, attacking the privileged position of the wealthy.Watson's 1785 sermon entitled 'The Wisdom and Goodness of God, in having made both Rich and Poor', defended economic inequality as divinely supported.