⊢

⊢ developed from ⊦, used to signify assertions in Principia Mathematica; in turn derived from idiosyncratic two-dimensional notation for logic employed in Begriffsschrift.

⊢

1. (logic) proves; it is provable

   ${\displaystyle {\mathsf {PA}}\vdash \forall a\ \forall b:a+b=b+a}$

• ⊬

• ⊨