A paradox arising from the question of what constitutes evidence for a statement. Observing objects that are neither black nor ravens may formally increase the likelihood that all ravens are black, even though, intuitively, these observations are unrelated.

Hempel's paradox

A thought experiment involving a game between two players, one of whom purports to be able to predict the future. The first player has to try to maximize winnings by choosing one of two boxes of money; however, the amount won also depends on whether a prediction made about the choice by the other player proves to be true.

A particular paradox in mathematical logic; the type-theoretic analogue of Russell's paradox from set theory.

plural of Epimenides paradox

A form of self-referential logical paradox associated with statements of the form "All Cretans are liars" (spoken by Epimenedes, himself a Cretan, who must therefore be lying).

Synonym of unexpected hanging paradox

Alternative letter-case form of Fermi paradox

(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.

The observation that at the species level, the incidence of cancer does not appear to correlate with the number of cells in an organism.