Paul-Henri Thiry was a French philosopher of the Enlightenment era, best known for his work titled "Letters on the English." Some synonyms for the name could include Baron d'Holbach, who was a close friend and collaborator of Thiry's, or simply Holbach as he is often referred to. Other potential synonyms might include influential Enlightenment philosophers like Voltaire, Rousseau, and Diderot, who all had an impact on Thiry's thinking. Alternatively, one could use synonyms for Thiry's areas of philosophy, such as atheism, materialism, and determinism, to describe him in a more meaningful way.