Kochen and Specker developed in the 1960s an alternative to Birkhoff and von Neumann’s quantum logic based on partial Boolean algebras, called partial classical propositional logic, which has been recently revisited in studies of contextuality. Unlike more common quantum logics, in the language of the logic studied here, a new symbol is added to express a relation of commeasurability or compatibility. Seman tically, the binary connectives are partial functions, with the logical value of a connective defined only for compatible propositions. This dissertation explores partial algebras, partial Boolean algebras and the concept of validity that they originate, comparing the notions of validity in this logic with those in classical propositional logic. The logical calculus of Kochen and Specker, which axiomatizes validity in partial classical propositional logic, is also studied. The theorems of soundness and completeness are proven, establishing an equivalence between both ways of characterizing the validity of this logic.