Knowledge signifies things known. Where there are no things known, there is no knowledge. Where there are no things to be known, there can be no knowledge. We have observed that every science, that is, every branch of knowledge, is compounded of certain facts, of which our sensations furnish the evidence. Where no such evidence is supplied, we are without data; we are without first premises; and when, without these, we attempt to build up a science, we do as those who raise edifices without foundations. And what do such builders construct? Castles in the air.

Equality! Where is it, if not in education? Equal rights! They cannot exist without equality of instruction.

He who lives in the single exercise of his mental faculties, however usefully or curiously directed, is equally an imperfect animal with the man who knows only the exercise of muscles.

No man can see his own prejudices.

All that I say is, examine, inquire. Look into the nature of things. Search out the grounds of your opinions, the for and against. Know why you believe, understand what you believe, and possess a reason for the faith that is in you.

Truth is but approved facts.

If we bring not the good courage of minds covetous of truth, and truth only, prepared to hear all things, and decide upon all things, according to evidence, we should do more wisely to sit down contented in ignorance, than to bestir ourselves only to reap disappointment.