"He who lets the world, or his own portion of it, choose his plan of life for him, has no need of any other faculty than the ape-like one of imitation."

"He who knows only his own side of the case knows little of that."

"The grand, leading principle, towards which every argument unfolded in these pages directly converges, is the absolute and essential importance of human development in its richest diversity."

"Men are not more zealous for truth than they often are for error, and a sufficiently frequent repetition of error, if not contradicted, passes for truth."

"The principle itself of dogmatic religion, dogmatic morality, dogmatic philosophy, is what requires to be rooted out."