What did the Enlightenment thinkers believe to be the sources of freedom ?
Historians generally are a bit uncomfortable with generalizing about something as broad as the European Enlightenment. There were many different strands of thought that characterized the Enlightenment, varying across countries and over time. In other words, you would have to specify which Enlightenment, or which Enlightenment thinker, you were talking about for a very precise answer. That said, most philosophes followed the seventeenth-century thinker John Locke in his belief that humans in their natural state were free. The need for safety and society caused people to give up their freedoms in what has become known as a social contract. Different Enlightenment thinkers characterized this social contract in different ways, with Jean-Jacques Rousseau being perhaps the most radical, but most accepted that government was created by the consent of free men. The crucial point here is that government in theory was charged only with protecting the rights of men. It did not create them. In other words, the source of freedom was not government, but humanity itself. People, because they were people, were free. Some of the philosophes argued that freedom thus came from the Creator, while others took a more secular view.