Philosophy in the Boudoir is a 1795 book by the Marquis de Sade written in the form of a dramatic dialogue. Set in a boudoir the two lead characters make the argument that the only moral system that reinforces the recent political revolution is libertinism, and that if the people of France fail to adopt the libertine philosophy, France will be destined to return to a monarchic state. In the chapter titled "Fifth Dialogue", there is a lengthy section where the character Chevalier reads a philosophical pamphlet titled "Frenchmen, Some More Effort If You Wish To Become Republicans". The pamphlet clearly represents Sade's philosophy on religion and morality, a philosophy he passionately hopes the citizens of France will embrace and codify into the laws of their new republican government. Continually throughout the work, Sade makes the argument that one must embrace atheism, reject society's beliefs about pleasure and pain, and further makes his argument that if any crime is committed while seeking pleasure, it cannot be condemned.

Donatien Alphonse François, Marquis de Sade was a French writer, libertine, political activist and nobleman best known for his libertine novels and imprisonment for sex crimes, blasphemy and pornography. His works include novels, short stories, plays, dialogues, and political tracts. Some of these were published under his own name during his lifetime, but most appeared anonymously or posthumously.