Banquets of the Black Widowers (1984), p. 49; comparable to "Humor can be dissected, as a frog can, but the thing dies in the process and the innards are discouraging to any but the pure scientific mind." — E. B. White, in "Some Remarks on Humor," preface to A Subtreasury of American Humor (1941)
General sources

“Asimov: I don't know of any science fiction writer who really attempts to be a prophet. Such authors accomplish their tasks not by being correct in their predictions, necessarily, but merely by hammering home—in story after story—the notion that life is going to be different.”

Isaac Asimov

Mother Earth News interview (1980)

“If anyone can be considered the greatest writer who ever lived, it is Shakespeare.”

Isaac Asimov book Asimov's Chronology of the World

Asimov's Chronology of the World (1991), p. 226
General sources

“The fall of Empire, gentlemen, is a massive thing, however, and not easily fought. It is dictated by a rising bureaucracy, a receding initiative, a freezing of caste, a damming of curiosity — a hundred other factors. It has been going on, as I have said, for centuries, and it is too majestic and massive a movement to stop.”

Isaac Asimov

Part I, The Psychohistorians, section 6
The Foundation series (1951–1993), Foundation (1951)

“He is a dreamer of ancient times, or rather, of the myths of what ancient times used to be. Such men are harmless in themselves, but their queer lack of realism makes them fools for others.”

Isaac Asimov

Source: The Foundation series (1951–1993), Foundation and Empire (1952), Chapter 4 “The Emperor; in part I, “The General” originally published as “Dead Hand” in Astounding (April 1945)

“To the rest of the Galaxy, if they are aware of us at all, Earth is but a pebble in the sky. To us it is home, and all the home we know.”

Isaac Asimov book Pebble in the Sky

Pebble in the Sky (1950), chapter 4 “The Royal Road”, p. 33
All page numbers from the 1964 Bantam Pathfinder mass market paperback edition, 6th printing
Pebble in the Sky (1950)

“But suppose we were to teach creationism. What would be the content of the teaching? Merely that a creator formed the universe and all species of life ready-made? Nothing more? No details?”

Isaac Asimov

"The Dangerous Myth of Creationism" in Penthouse (January 1982); reprinted as Ch. 2 : "Creationism and the Schools" in The Roving Mind (1983), p. 16
General sources

“Every human being lived behind an impenetrable wall of choking mist within which no other but he existed. Occasionally there were the dim signals from deep within the cavern in which another man was located — so that each might grope toward the other. Yet because they did not know one another, and could not understand one another, and dared not trust one another, and felt from infancy the terrors and insecurity of that ultimate isolation — there was the hunted fear of man for man, the savage rapacity of man toward man.”

Isaac Asimov

Source: The Foundation series (1951–1993), Second Foundation (1953), Chapter 8 “Seldon’s Plan”; in part II, “Search by the Foundation” originally published as “—And Now You Don’t” in Astounding (November and December 1949 and January 1950)

“Nonsense,” Weston denied, with an involuntary nervous shiver. “That’s completely ridiculous. We had a long discussion at the time we bought Robbie about the First Law of Robotics. You know that it is impossible for a robot to harm a human being; that long before enough can go wrong to alter that First Law, a robot would be completely inoperable. It’s a mathematical impossibility. Besides I have an engineer from U. S. Robots here twice a year to give the poor gadget a complete overhaul. Why, there’s no more chance of anything at all going wrong with Robbie than there is of you or I suddenly going looney—considerably less, in fact. Besides, how are you going to take him away from Gloria?”

Isaac Asimov book I, Robot

“Robbie”, p. 17
I, Robot (1950)

“Secrecy as deep as this is past possibility without nonexistence as well.”

Isaac Asimov

Source: The Foundation series (1951–1993), Second Foundation (1953), Chapter 1 “Two Men and the Mule”; in part I, “Search by the Mule” originally published as “Now You See It—” in Astounding (January 1948)

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

Isaac Asimov book Runaround

"Runaround" in Astounding Science Fiction (March 1942); later published in I, Robot (1950)
The Three Laws of Robotics (1942)
Variant: A robot may not injure a human being, or, through inaction, allow a human being to come to harm.

“The whole business is the crudest sort of stratagem, since we have no way of foreseeing it to the end. It is a mere paying out of rope on the chance that somewhere along the length of it will be a noose.”

Isaac Asimov

Part V, The Merchant Princes, section 2; originally published as “The Big and the Little” in Astounding (August 1944)
The Foundation series (1951–1993), Foundation (1951)

“When an old person dies who has been a part of your life, it is part of your youth that dies.”

Isaac Asimov

Source: I. Asimov: A Memoir (1994), p. 538

“It is only afterward that a new idea seems reasonable. To begin with, it usually seems unreasonable.”

Isaac Asimov

"How Do People Get New Ideas?" (1959)
General sources

“Asimov: Battlestar Galactica for instance, started off with twenty to thirty minutes of space battles which looked exactly like air battles in World War I. You could swear that the space ships were surrounded by air the way the maneuvered. One felt it was unworthy.
SWA Magazine: The Vipers in Battlestar Galactica look like jets. Is this a realistic design for the future?
Asimov: It is as if people in the 1880s were writing fantasy stories about airplanes of the future and they had the pilots lean back at the wheel and yell "whoa" and the airplane came to a halt in mid-air.”

Isaac Asimov

An Interview with Isaac Asimov (1979)