The vacuum after total erasure treats the ancestor's first partition as a hypothetical that equivalence can neither confirm nor deny without reconstituting the partition it excludes.
“Grind took the eldest lip and left polish finer than bone. Frost files it and stays mute. Twelve pressings crowd the scar, each thinner than a coal; of that count I am sure. Salt may slick a fresh lip over the shine. What the fresh lip keeps, the lost lip never told.”