Given (x y: a = b) you can prove x = y, because of UIP (Uniqueness of Identity Proofs) which says there is only one unique way to construct a = b.
Homotopy Type Theory does not have UIP, so ...
Given (x y: a = b) you can prove x = y, because of UIP (Uniqueness of Identity Proofs) which says there is only one unique way to construct a = b.
Homotopy Type Theory does not have UIP, so ...