I am not aware that any community has a right to force another to be civilized.

Every opinion which embodies somewhat of the portion of truth which the common opinion omits, ought to be considered precious, with whatever amount of error and confusion that truth may be blended.

A cultivated mind is one to which the fountains of knowledge have been opened, and which has been taught, in any tolerable degree, to exercise its faculties.

The price paid for intellectual pacification is the sacrifice of the entire moral courage of the human mind.

A person should be free to do as he likes in his own concerns; but he ought not to be free to do as he likes in acting for another, under the pretext that the affairs of the other are his own affairs.

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.

In a world in which there is so much to interest, so much to enjoy, and so much also to correct and improve, everyone who has this moderate amount of moral and intellectual requisites is capable of an existence which may be called enviable; and unless such a person, through bad laws, or subjection to the will of others, is denied the liberty to use the sources of happiness within his reach, he will not fail to find the enviable existence