Formulae are the anaesthetics of thought, not its stimulants and to make any one think is far better worth while than cramming him with ill-considered, and therefore indigestible, learning.

The whole object of science is to synthesize, and so simplify; and did we but know the uttermost of a subject we could make it singularly clear.

Are physical forces alone at work there, or has evolution begotten something more complex, something not akin to what we know on Earth as life? It is in this that lies the peculiar interest of Mars.

Imagination is as vital to any advance in science as learning and precision are essential for starting points. Let me warn you to beware of two opposite errors: of letting your imagination soar unballasted by facts, but on the other hand, of shackling it so solidly that it loses all incentive to rise.

Bright points in the sky or a blow on the head will equally cause one to see stars.

That Mars is inhabited by beings of some sort or other we may consider as certain as it is uncertain what these beings may be.

Now when we think that each of these stars is probably the centre of a solar system grander than our own, we cannot seriously take ourselves to be the only minds in it all.