A fire-eater must eat fire even if he has to kindle it himself.

Do not forget that a traitor within our ranks, known to us, can do more harm to the enemy than a loyal man can do good to us.

Creationists make it sound as though a 'theory' is something you dreamt up after being drunk all night.

What I will be remembered for are the Foundation Trilogy and the Three Laws of Robotics. What I want to be remembered for is no one book, or no dozen books. Any single thing I have written can be paralleled or even surpassed by something someone else has done. However, my total corpus for quantity, quality and variety can be duplicated by no one else. That is what I want to be remembered for.

[Social] science fiction is that branch of literature which is concerned with the impact of scientific advance on human beings.

Tell me why the stars do shine, Tell me why the ivy twines, Tell me what makes skies so blue, And I'll tell you why I love you. Nuclear fusion makes stars to shine, Tropisms make the ivy twine, Raleigh scattering make skies so blue, Testicular hormones are why I love you.

The world of A.D. 2014 will have few routine jobs that cannot be done better by some machine than by any human being. Mankind will therefore have become largely a race of machine tenders.