Written in 1746, without author's name, and immediately condemned to fire by the Paris Parliament, the Philosophical Thoughts take part in Christianity, and beyond all revealed religions: or faith is compatible with human reason and religions must accept doubt and criticism and reform themselves to join "natural religion"; or it is not, and how to admit then that God demand men to sacrifice their reason for him? This alternative is that posed by deism, with the will to place reason at the heart of religious systems (dogmas, beliefs, testimonies, miracles, Holy Books, etc.). While the Enlightenment is generally credited with laying the philosophical foundations of tolerance and secularism, the role played by deism in the fight against faith and reason is most often ignored. The Philosophical Thoughts, a subtle book that mobilizes all the resources of style to make the reader his ally, is the first philosophical work to focus on the public place the debate that opposes deists to the supporters of established religions.