Metamath Proof Explorer


Syntax definition walsi

Description: Extend wff definition to include "all some" applied to a top-level implication, which means ps is true whenever ph is true, and there is at least least one x where ph is true. (Contributed by David A. Wheeler, 20-Oct-2018)

Ref Expression
Assertion walsi wff ∀! 𝑥 ( 𝜑𝜓 )