Cat-Ideas and Mouse-Ideas. We can never get rid of mouse-ideas completely, they keep turning up again and again, and nibble, nibble-no matter how often we drive them off. The best way to keep them down is to have a few good strong cat-ideas which will embrace them and ensure their not reappearing till they do so in another shape.

The foundations which we would dig about and find are within us, like the kingdom of heaven, rather than without.

Inspiration is never genuine if it is known as inspiration at the time. True inspiration always steals on a person; its importance not being fully recognized for some time.

Though analogy is often misleading, it is the least misleading thing we have.

If [science] tends to thicken the crust of ice on which, as it were, we are skating, it is all right. If it tries to find, or professes to have found, the solid ground at the bottom of the water it is all wrong. Our business is with the thickening of this crust by extending our knowledge downward from above, as ice gets thicker while the frost lasts; we should not try to freeze upwards from the bottom.

Spare the rod and spoil the child.

The youth of an art is, like the youth of anything else, its most interesting period.