A choice problem designed to show an inconsistency of actual observed choices with the predictions of expected utility theory.

A paradox of choice in which people's decisions produce inconsistencies with subjective expected utility theory.

(philosophy) A philosophical problem whereby a man intends to walk a mile from a particular point, but an infinity of gods separately plan to obstruct him. One of them will raise a barrier to stop his further advance if he reaches the half-mile point, a second if he reaches the quarter-mile point, a third if he goes one-eighth of a mile, and so on ad infinitum. The paradox involves the fact that (i) the man cannot begin walking, because a barrier will stop him even at the shortest distance, but (ii) if he does not begin walking, no barrier will rise.

(philosophy) Any of a set of philosophical problems generally thought to have been devised by the Greek philosopher Zeno of Elea (c. 490–430 BC) to support Parmenides' doctrine that, contrary to the evidence of one's senses, the belief in plurality and change is mistaken, and in particular that motion is nothing but an illusion.

(relativity) The phenomenon in which two observers who start together with identical clocks, follow different timelines, and then rejoin can have different elapsed times on their clocks, especially if one travels at a relativistic speed.

(relativity) The clock paradox.

(astronomy) The observation that the night sky is mostly dark, yet, in a boundless universe of stars, every line of sight from the eye must eventually intercept the surface of a star.

A paradox, related to probability, where the expected win for repeated play of a game is infinite, so it seems that a player should be willing to pay any price to take part.

(biology) The apparent paradox that additive genetic variation is maintained despite persistent female choice for particular male traits.

The phenomenon of an arrow travelling in the direction where it points when the bow is fully drawn, when it seems that the arrow would have to pass through its original position. The explanation relates to the bending of the arrow when released.