The crows maintain that a single crow could destroy the heavens. There is no doubt of that, but it proves nothing against the heavens, for heaven simply means: the impossibility of crows.
Every spirit builds itself a house; and beyond its house, a world; and beyond its world a heaven. Know then, that the world exists for you: build, therefore, your own world.
I speak of that learning which wakes us acquainted with the boundless extent of nature, and the universe, and which even while we remain in this world, discovers to us both heaven, earth, and sea.
Without going outside, you may know the whole world, without looking through the window, you may see the ways of heaven. The farther you go, the less you know. Thus the sage knows without traveling; he sees without looking; he works without doing.