|Description: Definition of the truth
value "true", or "verum", denoted by ⊤.
This is a tautology, as proved by tru 1247. In this definition, an
instance of id 19 is used as the definiens, although any
as an axiom, can be used in its place. This particular id 19
was chosen so this definition can be checked by the same algorithm that
is used for predicate calculus. This definition should be referenced
directly only by tru 1247, and other proofs should depend on tru 1247
(directly or indirectly) instead of this definition, since there are
many alternative ways to define ⊤.
(Contributed by Anthony Hart,
13-Oct-2010.) (Revised by NM, 11-Jul-2019.)
(New usage is discouraged.)|