“The hardest theme in science fiction is that of the alien. The simplest solution of all is in fact quite profound—that the real difficulty lies not in understanding what is alien, but in understanding what is self. We are all aliens to each other, all different and divided. We are even aliens to ourselves at different stages of our lives. Do any of us remember precisely what it was like to be a baby?”

Source: Plague from Space (1965), Chapter 13 (p. 136)

“That’s hardly a basis for speculation now. It explains everything and nothing.”

Chapter 2 “The Hold” (p. 70)
Four Hundred Billion Stars (1988)

Source: Hainish Cycle, Planet of Exile (1966), Chapter 4 (The Tall Young Men)

Address to United Nations General Assembly http://www.reagan.utexas.edu/archives/speeches/1987/092187b.htm (21 September 1987)
1980s, Second term of office (1985–1989)
Context: Cannot swords be turned to plowshares? Can we and all nations not live in peace? In our obsession with antagonisms of the moment, we often forget how much unites all the members of humanity. Perhaps we need some outside, universal threat to make us recognize this common bond. I occasionally think how quickly our differences worldwide would vanish if we were facing an alien threat from outside this world. And yet, I ask you, is not an alien force already among us? What could be more alien to the universal aspirations of our peoples than war and the threat of war?

Source: Light (2002), Chapter 2 “Gold Diggers of 2400 AD” (p. 16)

Source: Virtual Mercury House. Planetary & Interplanetary Events, p. 48

Source: Time is the Simplest Thing (1961), Chapter 32 (p. 249)