Psychic phenomena include psychokinesis, telepathy, clairvoyance, and precognition. Psychokinesis is the ability to move objects through the direct power of the mind, telepathy is the power to perceive the thoughts of others without the use of the senses, clairvoyance is the ability to perceive distant objects without the use of the senses, and precognition is the ability to see the future without the use of the senses.

The psychologist Terence Hines (Hines, 1988, 83) argues that gambling casinos and government-run lotteries provide a real-world test for the existence of psychic phenomena. Every roll of a pair of dice, every spin of a roulette wheel, every game of poker or blackjack, and every purchase of a lottery ticket is an opportunity or the operation of psychokinesis, telepathy, clairvoyance, or precognition. If these phenomena actually occurred, then one would expect that the earnings of casinos and lotteries would be affected. But in fact these earnings are exactly as the laws of chance predict. Does this fact provide a fair test for the existence of psychic phenomena? Some defenders of psychic phenomena argue that psychic powers cannot be used for personal gain. Does this argument amount to an ad hoc modification of the hypothesis underlying psychic phenomena? Is the argument plausible?