Hierarchy of semi-classical
The converse of arrows in the hierarchy of semi-
classical principles are conjectured not to be
derivable in HA.
The conjecture have been solved for
1, 2 levels,
which include all principles corresponding to
inductive inference and below.
It is still open for the higher levels. Maybe
The exact place of general LLPO is open.
However, it is well-known in the lowest level,