Full Idea
If a state is to enjoy and preserve liberty, everyone must be able to say what he thinks. In a free state, therefore, a citizen may speak and write anything not expressly forbidden by the laws.
Gist of Idea
Freedom of speech and writing, within the law, is essential to preserve liberty
Source
Baron de Montesquieu (The Spirit of the Laws (rev. 1757) [1748], 19.27)
A Reaction
A commonplace now, but fairly bold then. I blame Freeborn John Lilburne for wild ideas like these.
Book Reference
Montesquieu,Baron de: 'Selected Political Writings', ed/tr. Richter,Melvin [Hackett 1990], p.222