Let
be a nontrivial bounded lattice (or a nontrivial complemented lattice, etc.). If
every nonconstant lattice homomorphism defined on
is
-separating, then
is a
-simple lattice.
One can show that the following are equivalent for a nontrivial bounded lattice :
1. The lattice
is
-simple;
2. There is a largest nontrivial congruence of
, and
satisfies both
and
.
This result is useful in the study of congruence lattices of finite algebras.