All over the world there are enormous numbers of smart, even gifted, people who harbor a passion for science. But that passion is unrequited. Surveys suggest that some 95 percent of Americans are “scientifically illiterate.” That’s just the same fraction as those African Americans, almost all of them slaves, who were illiterate just before the Civil War—when severe penalties were in force for anyone who taught a slave to read. Of course there’s a degree of arbitrariness about any determination of illiteracy, whether it applies to language or to science. But anything like 95 percent illiteracy is extremely serious.

— Carl Sagan

All science asks is to employ the same levels of skepticism we use in buying a used car or in judging the quality of analgesics or beer from their television commercials.

— Carl Sagan

All that we have seen is something of a vast and intricate and lovely universe. There is no particular theological conclusion that comes out of an exercise such as the one we have just gone through. What is more, when we understand something of the astronomical dynamics, the evolution of worlds, we recognize that worlds are born and worlds die, they have lifetimes just as humans do, and therefore that there is a great deal of suffering and death in the cosmos if there is a great deal of life.

— Carl Sagan

All the books in the world contain no more information than is broadcast as video in a single large American city in a single year. Not all bits have equal value.

— Carl Sagan

All the explanations proposed seem to be only partly satisfactory. They range from massive climatic change to mammalian predation to the extinction of a plant with apparent laxative properties, in which case the dinosaurs died of constipation.

— Carl Sagan

An atheist is someone who is certain that God does not exist, someone who has compelling evidence against the existence of God. I know of no such compelling evidence. Because God can be relegated to remote times and places and to uptime causes, we would have to know a great deal more about the Universe than we do now to be sure that no such God exists. To be certain of the existence of God and you be certain of the nonexistence of God seem to me to be the confident extremes in a subject so riddled with doubt and uncertainty as to inspire very little confidence indeed.

— Carl Sagan

An atheist is someone who is certain that God doesn't exist, someone who has compelling evidence against the existence of God. I know of no such compelling evidence.

— Carl Sagan

And despite the insignificance of the instant we have so far occupied in cosmic time, it is clear that what happens on and near Earth at the beginning of the second cosmic year will depend very much on the scientific wisdom and the distinctly human sensitivity of mankind.

— Carl Sagan

And reading itself is an amazing activity: You glance at a thin, flat object made from a tree...and the voice of the author begins to speak inside your head. (Hello!)

— Carl Sagan

And yet, the chief deficiency I see in the skeptical movement is in its polarization: Us v. Them - the sense that we have a monopoly on the truth; that those other people who believe in all these stupid doctrines are morons; that if you're sensible, you'll listen to us; an if not, you're beyond redemption. This is unconstructive. It does not get the message across. It condemns the skeptics to permanent minority status; whereas, a compassionate approach that from the beginning acknowledges the human roots of pseudoscience and superstition might be much more widely accepted.

— Carl Sagan