The appearance of strength is all about you. It would seem to last forever. However... the rotten tree-trunk, until the very moment when the storm-blast breaks it in two, has all the appearance of might it ever had. The storm-blast whistles through the branches of the Empire even now. Listen... and you will hear the creaking.

The final end of Eternity, and the beginning of Infinity

It is quite clear that as long as the nations of the world spend most of their energy, money, and emotional strength in quarreling with words and weapons, a true offensive against the common problems that threaten human survival is not very likely. A world government that can channel human efforts in the direction of the great solutions seems desirable, even essential. Naturally, such a world government should be a federal one, with regional and local autonomy safeguarded and with cultural diversity promoted.

It is in meeting the great tests that mankind can most successfully rise to great heights. Out of danger and restless insecurity comes the force that pushes mankind to newer and loftier conquests.

Before another century is done it will be hard for people to imagine a time when humanity was confined to one world, and it will seem to them incredible that there was ever anybody who doubted the value of space and wanted to turn his or her back on the Universe.

All of a sudden, space isn't friendly. All of a sudden, it's a place where people can die. . . . Many more people are going to die. But we can't explore space if the requirement is that there be no casualties; we can't do anything if the requirement is that there be no casualties.

It's the writing that teaches you.