Men can intoxicate themselves with ideas as effectually as with alcohol or with bang and produce, be dint of serious thinking, mental conditions hardly distinguishable from monomania.

Even in the important matter of cranial capacity, Men differ more widely from one another than they do from the Apes; while the lowest Apes differ as much, in proportion, from the highest, as the latter does from Man.

If a man cannot see a church, it is preposterous to take his opinion about its altar-piece or painted window.

To quarrel with the uncertainty that besets us in intellectual affairs would be about as reasonable as to object to live one's life with due thought for the morrow because no man can be sure he will alive an hour hence.

Whatever part of the animal fabric whatever series of muscles, whatever viscera might be selected for comparison the result would be the same the lower Apes and the Gorilla would differ more than the Gorilla and the Man.

No slavery can be abolished without a double emancipation, and the master will benefit by freedom more than the freed-man.

I wish you would let an old man, who has had his share of fighting, remind you that battles, like hypotheses, are not to be multiplied beyond necessity.

The doctrine of transmigration… was a means of constructing a plausible vindication of the ways of the cosmos to man; … none but very hasty thinkers will reject it on the grounds of inherent absurdity.

The only question which any wise man can ask himself, and which any honest man will ask himself, is whether a doctrine is true or false.