Logic

Named arguments and positions that concern valid inference, the foundations of formal reasoning and paradoxes internal to a logical or mathematical system: Russell's paradox as the set-theoretic contradiction that reshaped the foundations of mathematics and logic in the early twentieth century. Belongs here: a formulated argument or paradox whose target is the consistency or structure of a formal system itself. Does not belong here: an argument that merely uses logical form to reach a metaphysical or epistemological conclusion, grouped under Metaphysics or Epistemology instead.