"If some authority were to be granted the power to regulate [opinions], it would very soon abuse such power. And whom would be put in charge of prohibiting us from erring? Him who is exempt from it? But governments do not find themselves in this category.
Quite the contrary, when the causes are sought which have done most to spread error and contribute to perpetuating it, they are always found in prohibitive institutions. Moreover, if governments were authorized to prohibit all errors and to punish the stupid, the world would very soon be missing a great number of its men, the rest being reduced to eternal silence. We will be told that not all opinions must fall under the inspection of the authorities, but if one opinion is subjected to it, the rest are not secure; laws cannot make a precise classification, nor an exact enumeration, of all of them. Thus, such a power is necessarily arbitrary, and in most cases will become a reason for persecution. These are not unfounded suspicions; look back to the barbarous centuries and you will see universities, parliaments, chancelleries, and kings and queens determined to banish the wise who were making some discoveries in physics, and who were attacking the doctrines of Aristotle. Petrus Ramus, Johannes Trithemius, Galileo Galilei, and other luminaries, would go on to suffer what would not be believed if we did not possess solid proof of it. And what were the fruits of such proceedings? Did governments achieve what they intended? Not at all. The number of proselytes grew day after day, perhaps because of that very persecution."
"Indeed, if one wishes to lend credence to a doctrine, he need do nothing more than ban it. Men will of course suppose, and in this they are not mistaken, that it cannot be combated by reason when it is being attacked by force."