The witch in the fairy tale says, "Blow the horn, and the ogre's castle will fall"; but she does not say it as if it were something in which the effect obviously arose out of the cause.

Doubtless she has given the advice to many champions, and has seen many castles fall, but she does not lose either her wonder or her reason.

She does not muddle her head until it imagines a necessary mental connection between a horn and a falling tower.

But the scientific men do muddle their heads, until they imagine a necessary mental connection between an apple leaving the tree and an apple reaching the ground.

They do really talk as if they had found not only a set of marvellous facts, but a truth connecting those facts.