Proof of `Π_k is co-Σ_k` (2nd statement)
groundedproofs/Lax564036Proofs/Bridge.lean · lax-564036
What this proof establishes
no assumptions
Assuming the claims on the left, the claim on the right holds — checked by the archive's pipeline. Proof code is not displayed here.
Description
At level zero both sides are SO-Horn definability of the complement; above, the library's duality of the two kinds of second-order sentences.