Veridical paradox

A veridical paradox produces a result that appears absurd, but is demonstrated to be true nonetheless.

• The paradox of Frederic's birthday in The Pirates of Penzance establishes the surprising fact that a twenty-one-year-old would have had only five birthdays had he been born on a leap day.
• Likewise, Arrow's impossibility theorem demonstrates difficulties in mapping voting results to the will of the people.
• Monty Hall paradox (or equivalently three prisoners problem) demonstrates that a decision that has an intuitive fifty–fifty chance is in fact heavily biased towards making a decision that, given the intuitive conclusion, the player would be unlikely to make.
• In 20th-century science, Hilbert's paradox of the Grand Hotel, Schrödinger's cat, Wigner's friend or the Ugly duckling theorem are famously vivid examples of a theory being taken to a logical but paradoxical end.