“For our improvement we need a mirror.”

Kiichiro Toyoda in The Toyota Way, 2001: Quoted in: "Toyota quotes," New York Times, Feb. 10, 2008.
Comment by Kiichiro Toyoda after thieves had stolen the plans for a new loom from his father's workshop.

Source: Solaris

Source: Solaris

Humboldt's Gift (1975), p. 265
General sources

Source: Solaris (1961), Ch. 6: "The Little Apocrypha", p. 72
Context: We are only seeking Man. We have no need of other worlds. We need mirrors. We don't know what to do with other worlds. A single world, our own, suffices us; but we can't accept it for what it is. We are seaching for an ideal image of our own world: we go in quest of a planet, of a civilisation superior to our own but developed on the basis of a prototype of our primeval past. At the same time, there is something inside us which we don't like to face up to, from which we try to protect ourselves, but which nevertheless remains, since we don't leave Earth in a state of primal innocence. We arrive here as we are in reality, and when the page is turned and that reality is revealed to us — that part of our reality which we would prefer to pass over in silence — then we don't like it any more.

Source: I Know This Much Is True

Marius Melville in Ch. 17
Cassidy (1986)

Source: The Face of Another

Source: Aphorisms and Reflections (1901), p. 31