The paradox index
Explore our alphabetical compendium of humanity's most intriguing contradictions, logical puzzles, and philosophical dilemmas. Step into the riddles that challenge the boundaries of reality, language, and thought.
Fermi paradox
In an ancient universe vast enough for billions of civilizations, where is everyone?
If intelligent life is a natural outcome of cosmic evolution across countless star systems, the silence of the night sky presents an unsettling riddle. Does the lack of contact point to rare beginnings, self-destruction, or our own blindness?
Grandfather paradox
Can time travel allow past actions to erase the very conditions of the traveller's existence?
Step backwards into history and alter a critical moment before your ancestors meet. If you cease to exist, who ever travelled back to alter the past? This timeless puzzle exposes the thorny nature of causality and temporal logic.
Ship of Theseus
When every plank of a vessel has been replaced over time, is it genuinely the same original craft?
As parts decay and renewed timber takes their place, the boundary between continuity and total transformation dissolves. Contemplate the nature of identity, matter, and the persistence of being through relentless change.
The liar paradox
"This statement is false."
If the statement is true, then according to its own assertion, it must be false. Yet if it is false, then what it asserts is actually true. Originating from ancient thinkers like Epimenides and Eubulides, this self-referential riddle strikes at the very foundations of truth, logic, and formal language.
Have questions about philosophical riddles?
Delve deeper into the nature of logical dilemmas, thought experiments, and truth. Read our answers to common questions or learn how these puzzles shape modern science and philosophy.