Many of the most influential philosophers of that time, like the Encyclopédistes, Voltaire or Reimarus, were secularists or promoted a deist view: In a nutshell, they proclaimed that nature was the only revelation God has ever made and thus the preoccupation with any other alleged revelation was superfluous.
He was a rationalist (free-thought) lecturer and was involved with the English Secularists and obtained a diploma from the National Secular Society.