Over one's mind and over one's body the individual is sovereign.

The principle itself of dogmatic religion, dogmatic morality, dogmatic philosophy, is what requires to be rooted out; not any particular manifestation of that principle. The very corner-stone of an education intended to form great minds, must be the recognition of the principle, that the object is to call forth the greatest possible quantity of intellectual power, and to inspire the intensest love of truth.

The perpetual obstacle to human advancement is custom.

Popular opinions, on subjects not palpable to sense, are often true, but seldom or never the whole truth.

In this age, the man who dares to think for himself and to act independently does a service to his race.

There is always need of persons not only to discover new truths, and point out when what were once truths are true no longer, but also to commence new practices, and set the example of more enlightened conduct, and better taste and sense in human life.

...there ought to exist the fullest liberty of professing and discussing, as a matter of ethical conviction, any doctrine, however immoral it may be considered.