“When you look more generally at life on Earth, you find that it is all the same kind of life. There are not many different kinds; there's only one kind. It uses about fifty fundamental biological building blocks, organic molecules.”

“The Earth is the only world known so far to harbour life. There is nowhere else, at least in the near future, to which our species could migrate. Visit? Yes. Settle? Not yet. Like it or not, for the moment, the Earth is where we make our stand. It has been said that astronomy is a humbling and character-building experience. ... To me, it underscores our responsibility to deal more kindly with one another and to preserve, and cherish, the pale blue dot; the only home we've ever known.”

“If we are to discuss the idea of God and be restricted to rational arguments, then it is probably useful to know what we are talking about when we say “God.” This turns out not to be easy. The Romans called the Christians atheists. Why? Well, the Christians had a god of sorts, but it wasn’t a real god. They didn’t believe in the divinity of apotheosized emperors or Olympian gods. They had a peculiar, different kind of god. So it was very easy to call people who believed in a different kind of god atheists. And that general sense that an atheist is anybody who doesn’t believe exactly as I do prevails in our own time.”

“Frederick Douglass taught that literacy is the path from slavery to freedom. There are many kinds of slavery and many kinds of freedom, but reading is still the path.”

“There are as many atoms in one molecule of DNA as there are stars in a typical galaxy.”

“I find many adults are put off when young children pose scientific questions. Why is the Moon round? the children ask. Why is grass green? What is a dream? How deep can you dig a hole? When is the world’s birthday? Why do we have toes? Too many teachers and parents answer with irritation or ridicule, or quickly move on to something else: ‘What did you expect the Moon to be, square?’ Children soon recognize that somehow this kind of question annoys the grown-ups. A few more experiences like it, and another child has been lost to science. Why adults should pretend to omniscience before 6-year-olds, I can’t for the life of me understand. What’s wrong with admitting that we don’t know something? Is our self-esteem so fragile?”

“I am a collection of water, calcium and organic molecules called Carl Sagan. You are a collection of almost identical molecules with a different collective label. But is that all? Is there nothing in here but molecules? Some people find this idea somehow demeaning to human dignity. For myself, I find it elevating that our universe permits the evolution of molecular machines as intricate and subtle as we.But the essence of life is not so much the atoms and simple molecules that make us up as the way in which they are put together. Every now and then we read that the chemicals which constitute the human body cost ninety-seven cents or ten dollars or some such figure; it is a little depressing to find our bodies valued so little. However, these estimates are for human beings reduced to our simplest possible components. We are made mostly of water, which costs almost nothing; the carbon is costed in the form of coal; the calcium in our bones as chalk; the nitrogen in our proteins as air (cheap also); the iron in our blood as rusty nails. If we did not know better, we might be tempted to take all the atoms that make us up, mix them together in a big container and stir. We can do this as much as we want. But in the end all we have is a tedious mixture of atoms. How could we have expected anything else?”