Final answer:
Voltaire was a fervent advocate for religious tolerance and freedom of speech, using his writings to express these ideas during the Enlightenment. Alongside other thinkers, his contributions significantly influenced the principles of religious liberty present in the U.S. Constitution.
Step-by-step explanation:
François-Marie d'Arouet, known by his pen name Voltaire, was especially vocal as an advocate of intrinsic rights and liberties. He critiqued institutions like the Catholic Church, the aristocracy, and the French monarchy, championing religious toleration, freedom of speech, and the power of reason. Through works like Treatise on Tolerance and Republican Ideas, as well as his satire Candide, Voltaire advanced his beliefs on these subjects. Voltaire believed deeply in the right of individuals to express their religious beliefs freely and the essential nature of open discourse in society.