“At my back I hear the word—”homosexual”—and it seems to split my world in two…. It is ignorance, our ignorance of one another, that creates this terrifying erotic chaos. Information, a crumb of information, seems to light the world.”

Variant translations: Are you really sure that a floor can't also be a ceiling?
I can't keep from fooling around with our irrefutable certainties. It is, for example, a pleasure knowingly to mix up two and three dimensionalities, flat and spatial, and to make fun of gravity.
1950's, On Being a Graphic Artist', 1953
Context: In my prints I try to show that we live in a beautiful and orderly world and not in a chaos without norms, as we sometimes seem to. My subjects are also often playful. I cannot help mocking all our unwavering certainties. It is, for example, great fun deliberately to confuse two and three dimensions, the plane and space, or to poke fun at gravity. Are you sure that a floor cannot also be a ceiling? Are you absolutely certain that you go up when you walk up a staircase? Can you be definite that it is impossible to eat your cake and have it?

Rich Dad Poor Dad: What the Rich Teach Their Kids About Money-That the Poor and the Middle Class Do Not!

Source: Warbreaker

Vol. I; I
Lacon (1820)

Source: The Age of Missing Information (1992), p. 9

Mysterious Answers To Mysterious Questions http://lesswrong.com/lw/iu/mysterious_answers_to_mysterious_questions/ (August 2007); Yudkowsky credits the map/territory analogy to physicist/statistician Edwin Thompson Jaynes.

Source: 1880s, Incidents and Anecdotes of the Civil War (1885), p. 296

Source: LSD : My Problem Child (1980), Ch. 1 : How LSD Originated
Context: I was seized by the dreadful fear of going insane. I was taken to another world, another place, another time. My body seemed to be without sensation, lifeless, strange. Was I dying? Was this the transition? At times I believed myself to be outside my body, and then perceived clearly, as an outside observer, the complete tragedy of my situation. I had not even taken leave of my family (my wife, with our three children had traveled that day to visit her parents, in Lucerne). Would they ever understand that I had not experimented thoughtlessly, irresponsibly, but rather with the utmost caution, and that such a result was in no way foreseeable? My fear and despair intensified, not only because a young family should lose its father, but also because I dreaded leaving my chemical research work, which meant so much to me, unfinished in the midst of fruitful, promising development. Another reflection took shape, an idea full of bitter irony: if I was now forced to leave this world prematurely, it was because of this lysergic acid diethylamide that I myself had brought forth into the world.

1920s, The Aims of Education (1929)