God, how that stings! I've spent a lifetime loving science fiction and now I find that you must expect nothing of something that's just science fiction.

Intelligence is an extremely subtle concept. It's a kind of understanding that flourishes if it's combined with a good memory, but exists anyway even in the absence of good memory. It's the ability to draw consequences from causes, to make correct inferences, to foresee what might be the result, to work out logical problems, to be reasonable, rational, to have the ability to understand the solution from perhaps insufficient information. You know when a person is intelligent, but you can be easily fooled if you are not yourself intelligent.

It's humbling to think that all animals, including human beings, are parasites of the plant world.

Postulates are based on assumption and adhered to by faith. Nothing in the Universe can shake them.

Suppose that we are wise enough to learn and know - and yet not wise enough to control our learning and knowledge, so that we use it to destroy ourselves? Even if that is so, knowledge remains better than ignorance.

But life is glorious when it is happy; days are carefree when they are happy; the interplay of thought and imagination is far and superior to that of muscle and sinew. Let me tell you, if you don't know it from your own experience, that reading a good book, losing yourself in the interest of words and thoughts, is for some people (me, for instance) an incredible intensity of happiness.

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.