Why had we come to the moon? The thing presented itself to me as a perplexing problem. What is this spirit in man that urges him for ever to depart from happiness and security, to toil, to place himself in danger, to risk an even a reasonable certainty of death? It dawned upon me that there in the moon as a thing I ought always to have known, that man is not made to go about safe and comfortable and well fed and amused. ... against his interest, against his happiness, he is constantly being driven to do unreasonable things. Some force not himself impels him, and he must go.

If you are in difficulties with a book, try the element of surprise: attack it at an hour when it isn't expecting it.

There's truths you have to grow into.

Few people realise the immensity of vacancy in which the dust of the material universe swims.

I want to go ahead of Father Time with a scythe of my own.

I doubt if these two fine, active minds [President and Mrs. Roosevelt] have ever inquiried how it is they know what they know and think as they do. Nor have they ever thought of what they might have been if they had grown up in an entirely different culture. They have the disposition of all politicians world over to deal only with made opinion. They have never inquired how it is that opinion is made.

It is not much good thinking of a thing unless you think it out.