There are limits beyond which your folly will not carry you. I am glad of that. In fact, I am relieved.

Printing will tell you such useful things and such interesting things that not being able to read would be as bad as not being able to see.

The best way to describe anyone is to give an example of the kind of thing he would do.

It's my belief that the Universe possesses, in its essence, fractal properties of a very complex sort and that the pursuit of science shares those properties. It follows that any part of the Universe that remains un-understood, and any part of scientific investigation that remains unresolved, however small that might be in comparison to what is understood and resolved, contains within it all the complexity of the original. Therefore, we'll never finish. No matter how far we go, the road ahead will be as long as it was at the start, and that's the secret of the Universe.

Miniaturization doesn't actually make sense unless you miniaturize the very atoms of which matter is composed. Otherwise a tiny brain in a man the size of an insect, composed of normal atoms, is composed of too few atoms for the miniaturized man to be any more intelligent than the ant. Also, miniaturizing atoms is impossible according to the rules of quantum mechanics.

Modesty is an unnatural attitude, and one which is only with difficulty taught to children.

I am not a visual person. I have spent so many bounded years in my childhood that I have grown used to having books as my window on reality.

Writing is an addiction more powerful than alcohol, than nicotine, than crack. I could not conceive of not writing.

I am an atheist, out and out. It took me a long time to say it. I've been an atheist for years and years, but somehow I felt it was intellectually unrespectable to say one was an atheist, because it assumed knowledge that one didn't have. Somehow, it was better to say one was a humanist or an agnostic. I finally decided that I'm a creature of emotion as well as of reason. Emotionally, I am an atheist. I don't have the evidence to prove that God doesn't exist, but I so strongly suspect he doesn't that I don't want to waste my time.

I don't believe in an afterlife, so I don't have to spend my whole life fearing hell, or fearing heaven even more. For whatever the tortures of hell, I think the boredom of heaven would be even worse.

The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!', but 'That's funny ...'

People don't stop things they enjoy doing just because they reach a certain age. They don't stop playing tennis just because they turn 40, they don't stop with sex just because they turn 40; they keep it up as long as they can if they enjoy it, and learning will be the same thing.

The job of science will never be done, it will just sink deeper and deeper into never-ending complexity.

Titles are an important part of a story and I take considerable care in choosing one. In fact, I cannot start a story until I have chosen a title.

Self-preservation has frequently knuckled under to that tremendous yearning to get even.

Writing is hard work. The fact that I love doing it doesn't make it less hard work. People who love tennis will sweat themselves to exhaustion playing it, and the love of the game doesn't stop the sweating. The casual assumption that writers are unemployed bums because they don't go to the office and don't have a boss is something every writer has to live with. I have never known a writer who hasn't suffered as a result of this, hasn't resented it, and hasn't dreamed of murdering the next person who says "Boy, you've sure got it made. You just sit there and toss off a story or something whenever you feel like it."

Radiation, unlike smoking, drinking, and overeating, gives no pleasure, so the possible victims object.

Earth is a ball that is over 12,000 kilometres in diameter, and if it were modelled into an object the size of a billiard ball, with all its surface unevenness reproduced exactly to scale, the model would be smoother than an ordinary billiard ball and the ocean would be an all but unnoticeable mist of dampness over 70 percent of its surface.

A robot may not injure a human being, or, through inaction, allow a human being to come to harm.

Of all the cultural aspects of humanity, the only one which is not broken up into national or regional splinters is science. Different nations have different languages, they may have different religions, may have different dietaries, may have different holidays, different ways of thinking, but here's only one science. 

Often, writers on historical events tend to consider ... a loss of willingness to fight as a sign of "decadence," as though there were something despicable about not being a bully and not being willing to engage in mass murder. Perhaps we ought to feel instead that to cease to be warlike means to begin to be civilized and decent.

The history of science is full of revolutionary advances that required small insights that anyone might have had, but that, in fact, only one person did.

It is the nature of science that answers automatically pose new and more subtle questions.

I consider one of the most important duties of any scientist the teaching of science to students and to the general public.

Certain success evicts one from the paradise of winning against the odds.

It is important to remember that the viciousness and wrongs of life stick out very plainly but that even at the worst times there is a great deal of goodness, kindness, and day-to-day decency that goes unnoticed and makes no headlines.

Straightforward preaching spoils the effectiveness of a story. If you can't resist the impulse to improve your fellow human beings, do it subtly.

It is an odd fact that anyone who wishes to start a war must always make it appear that he is fighting in a just cause even if the real motive is naked aggression. Fortunately for the would-be aggressor, a "just cause" is very easy to find.

In memory yet green, in joy still felt, The scenes of life rise sharply into view. We triumph; Life's disasters are undealt, And while all else is old, the world is new.

The fact that the general incidence of leukemia has doubled in the last two decades may be due, partly, to the increasing use of x-rays for numerous purposes. The incidence of leukemia in doctors, who are likely to be so exposed, is twice that of the general public. In radiologists the incidence is ten times greater.

The true discovery of America by mankind came when those first hunting bands crossed over from Siberia 25,000 years ago. This, however, never seems to count. When people speak of the "discovery of America" they invariably mean its discovery by Europeans.

Weisinger, a couple of years ago, made up the following story: "Isaac Asimov was asked how Superman could fly faster than the speed of light, which was supposed to be an absolute limit. To this Asimov replied, 'That the speed of light is a limit is a theory; that Superman can travel faster than light is a fact.'"

Generals are usually a conservative force who can be relied on to oppose social change.

What, then, of human activities? Is humankind itself hastening its own end? Man has, for instance, been burning carbon-containing fuel — wood, coal, oil, gas — at a steadily accelerating rate. All these fuels form carbon dioxide. Some is absorbed by plants and the oceans but not as fast as it is produced. This means the carbon dioxide content of the air is going up — slightly but nevertheless up. Carbon dioxide retains heat, and even a small rise means a warming of the Earth's atmosphere. This may result in the melting of the polar ice caps with unusual speed, flooding the world before we have learned climate control. In reverse, our industrial civilization is making our atmosphere dustier so that it reflects more sunlight away and cools the Earth slightly — thus making possible a glacial advance in a few centuries, also before we have learned climate control.

People who want to do so can lose weight most safely and permanently if they realize that above all they must be patient. ... It is better to eat a little less at each meal than impulse would suggest and to do that constantly. Add to this a little more exercise or activity than impulse suggests and keep that up constantly too. A few less calories taken in each day and a few more used up will decrease weight, slowly, to be sure, but without undue misery. And with better long-range results too.

I recognize the necessity of animal experiments with my mind but not with my heart.

The military mind remains unparalleled as a vehicle of creative stupidity.

Indeed, it may well be argued that one reason for the decline in science, art, and literature was the increasing absorption of the better minds into a new sort of intellectual pursuit, theology.

There is no way of being almost funny or mildly funny or fairly funny or tolerably funny. You are either funny or not funny and there is nothing in between. And usually it is the writer who thinks he is funny and the reader who thinks he isn't.

Probably, the most-often-repeated lesson in history is that foreigners who are called in to help one side in a civil war take over for themselves. It is a lesson that seems never to be learned despite endless repetition.

I wouldn't give an astrologer the time of day.

By 1204, the only place where the entire body of Greek learning existed, still intact, was Constantinople. As a result of the crusaders' conquest, however, Constantinople was ruthlessly pillaged and destroyed and almost all the great treasures of ancient Greek learning were lost forever. It is because of that sack, for instance, that we have only seven plays left out of the better than one hundred written by Sophocles. The tragedy of 1204 can never be undone and for all of time, only bits and pieces of the marvelous Greek world can be known to us.

There is no belief, however foolish, that will not gather its faithful adherents who will defend it to the death.

When you write a short story ... you had better know the ending first. The end of a story is only the end to the reader. To the writer, it's the beginning. If you don't know exactly where you're going every minute you're writing, you'll never get there or anywhere.

In the world of today can there be peace anywhere until there is peace everywhere?

I believe that only scientists can understand the universe. It is not so much that I have confidence in scientists being right, but that I have so much in nonscientists being wrong.

The dullness of fact is the mother of fiction.

Inspect every piece of pseudoscience and you will find a security blanket, a thumb to suck, a skirt to hold. What does the scientist have to offer in exchange? Uncertainty! Insecurity!

It is very likely that there are many, many planets carrying life, even intelligent life, throughout the universe, because there are so many stars. By sheer chance, even if those chances are small, a great many life forms and a great many intelligences may exist.

When one plays for top prizes one must be prepared to pay top stakes.