The Dispossessed by Ursula K. LeGuin, Quotes, p. 314

As he started down, the air grumbled a little and he felt a strangeness: no jolt, no tremor, but a displacement, a conviction that things were wrong. He completed the step he had been making, and the ground was there to meet his foot. He went on; the road stayed laying down. He had been in no danger, but he had never in any danger known himself so close to death. Death was in him, under him; the earth itself was uncertain, unreliable. The enduring, the reliable, is a promise made by the human mind.