 Negation is a sine qua non of every human language, yet is absent from otherwise complex systems of animal  communication.[1]  While animal “languages” are essentially analog systems, it is the digital nature of the natural language negative operator, represented in Stoic and Fregean propositional logic as a one-place sentential connective toggling the truth value of statements between T[rue] and F[alse] (or 1 and 0) and applying recursively to its own output, that allows for denial, contradiction, and other key properties of human linguistic systems.