Full Idea
A 'theorem' of logic is the conclusion of a provable sequent in which the number of assumptions is zero.
Gist of Idea
A 'theorem' is the conclusion of a provable sequent with zero assumptions
Source
E.J. Lemmon (Beginning Logic [1965], 2.2)
Book Reference
Lemmon,E.J.: 'Beginning Logic' [Nelson 1979], p.50
A Reaction
This is what Quine and others call a 'logical truth'.
Related Idea
Idea 13689 'Theorems' are formulas provable from no premises at all [Sider]