primitive symbol

…parts: (1) a list of primitive symbols (basic units) given mechanically, (2) certain combinations of these symbols, singled out mechanically as forming the simple (atomic) sentences, and (3) a set of inductive clauses—inductive inasmuch as they stipulate that natural combinations of given sentences formed by such logical connectives as the…

…formation rules:

…are then said to be primitive. If “=_Df” is used to mean “is defined as,” then the relevant definitions can be set down as follows: (α · β) = _Df ∼(∼α ∨ ∼β)
(α ⊃ β) = _Df (∼α ∨ β)
(α ≡ β) = _Df [(α ⊃ β) · (β ⊃…