Language is the light of the mind

When one's ideas are not challenged, one's ability to defend them weakens.

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 application of algebra to geometry ... has immortalized the name of Descartes, and constitutes the greatest single step ever made in the progress of the exact sciences.

A state which dwarfs its men, in order that they may be more docile instruments in its hands even for beneficial purposes--will find that with small men no great thing can really be accomplished.

A state of things in which a large portion of the most active and inquiring intellects find it advisable to keep the genuine principles and grounds of their convictions within their own breasts, and attempt, in what they address to the public, to fit as much as they can of their own conclusions to premises which they have internally renounced, cannot send forth the open, fearless characters, and logical, consistent intellects who once adorned the thinking world.

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