The beliefs which we have most warrant for have no safeguard to rest on but a standing invitation to the whole world to prove them unfounded. If the challenge is not accepted, or is accepted and the attempt fails, we are far enough from certainty still; but we have done the best that the existing state of human reason admits of; we have neglected nothing that could give the truth a chance of reaching us.

Human beings are not like sheep; and even sheep are not undistinguishably alike. A man cannot get a coat or a pair oboots to fit him, unless they are either made to his measure, or he has a whole warehouseful to choose from: and is it easier to fit him with a life than with a coat, or are human beings more like one another in their whole physical and spiritual conformation than in the shape of their feet? If it were only that people have diversities of taste, that is reason enough for not attempting to shape them all after one model.

To think that because those who wield power in society wield in the end that of government, therefore it is of no use to attempt to influence the constitution of the government by acting on opinion, is to forget that opinion is itself one of the greatest active social forces. One person with a belief is a social power equal to ninety-nine who have only interests.

The most cogent reason for restricting the interference of government is the great evil of adding unnecessarily to its power.

The test of real and vigorous thinking, the thinking which ascertains truths instead of dreaming dreams, is successful application to practice.

To refuse a hearing to an opinion, because they are sure that it is false, is to assume that their certainty is the same thing as absolute certainty. All silencing of discussion is an assumption of infallibility.

The despotism of custom is everywhere the standing hindrance to human advancement.