Catch-22 – Situation in which one cannot avoid a problem because of contradictory constraints
Causal loop – Sequence of events which cause each other
Dilemma – Problem requiring a choice between equally undesirable alternatives
Euthyphro dilemma – Ethical problem on the origin of morality posed by Socrates
Grandfather paradox – Theoretical paradox resulting from time travel – Going back in time to kill one's own grandfather generates a circular contradiction
Hysteron proteron – Figure of speech reversing a natural or rational order
Klein bottle – Non-orientable mathematical surface
Mise en abyme – Technique of placing a copy of an image within itself, or a story within a story
Meno – Dialogue by Plato - Paradox: One must already possess any given piece of knowledge, otherwise it could not be recognized when supposedly "discovered"