Description: Define the well-founded
relation predicate. In the presence of excluded
middle, there are a variety of equivalent ways to define this. In our
case, this definition, in terms of an inductive principle, works better
than one along the lines of "there is an element which is minimal
when A
is ordered by R". Because is constrained to be a set (not a
proper class) here, sometimes it may be necessary to use FrFor
directly rather than via . (Contributed by Jim Kingdon and Mario
Carneiro, 21-Sep-2021.) |