plural of paradox of fiction

(philosophy) The paradox that (i) people have emotional responses to fictitious events, and (ii) one must believe that something truly exists in order to be emotionally moved by it, but (iii) nobody who considers an event to be fictitious can also believe it to be real.

(set theory) A demonstration of a surprising property of infinite sets. Some positive integers are squares while others are not; therefore, all the numbers, including both squares and non-squares, must be more numerous than just the squares; yet for every square there is exactly one positive number that is its square root, and for every number there is exactly one square; hence, there cannot be more of one than of the other.

(fluid dynamics) The contradiction that, for incompressible and inviscid potential flow, the drag force is zero on a body moving with constant velocity relative to the fluid.

(set theory) The paradox that a set defined to contain all sets which do not contain themselves can neither consistently contain itself nor not contain itself.

The observation that the French suffer a relatively low incidence of coronary heart disease, despite having a diet relatively rich in saturated fats.

The observation that the association of two variables for one subset of a population may be similar to the association of those variables in another subset, but different from the association of the variables in the total population.

(biology, exobiology) The seeming contradiction, serving as a challenge to believers in the existence of advanced lifeforms throughout the universe, that there is no scientific evidence that extraterrestrial civilizations have tried to visit or communicate with Earth.

plural of Klein paradox

A paradox that occurs in naive set theory or naive logics, and allows the derivation of an arbitrary sentence from a self-referring sentence and some apparently innocuous logical deduction rules.