"The only freedom, which consists in doing what one likes, is that of doing what one ought to like."

"The greatest dangers to liberty lurk in insidious encroachment by men of zeal, well-meaning but without understanding."

"The whole of mankind has a right to the benefit of the best ideas, which can only be produced by freedom of thought."

"The sole end for which mankind are warranted, individually or collectively, in interfering with the liberty of action of any of their number, is self-protection."

"The human mind, when it is in a healthy state, is never satisfied with having attained a certain measure of truth; it is always aspiring to a higher."