Fundamental to Spinoza's theory was the belief that all people have the inherent right to their own thoughts and opinions and in the impossibility of one's mind being controlled by another person.
"A sovereign is certainly free to try and limit what people think, but the result of such a policy, Spinoza predicts, would be only to create resentment and opposition to its rule." - Steven Nadler, "Spinoza’s Vision of Freedom, and Ours", New York Times, Feb 5 2012. http://opinionator.blogs.nytimes.com/2012/02/05/spinozas-vision-of-freedom-and-ours/
Spinoza, Baruch. "Theological-Political Treatise." (1670). Translated by S. Shirley, Indianapolis: Hackett Publishing Co, 2001.