diff --git a/SimpleCounterexamples/FinitudeOfPropositions.lean b/SimpleCounterexamples/FinitudeOfPropositions.lean new file mode 100644 index 0000000..12b8eb9 --- /dev/null +++ b/SimpleCounterexamples/FinitudeOfPropositions.lean @@ -0,0 +1,14 @@ +-- I actually thought that ∀p, ∃q, (q ≠ p) ∧ q! +-- However, propositional extensionality tells us that (p ↔ q) → p = q + +theorem finiteTrueProps + : ¬∀p, ∃q, (q ≠ p) ∧ q := by + intro h + have := h True + simp at this + +theorem finiteFalseProps + : ¬∀p, ∃q, (q ≠ p) ∧ ¬q := by + intro h + have := h False + simp at this