Verifiability theory of meaning
In the early twentieth century, the logical positivists put forth what came to be known as the verifiability theory of meaning.
Explanation
The verifiability theory was based upon the verifiability principle, which states
The statement is literally meaningful (it expresses a proposition) if and only if it is either analytic or empirically verifiable.
However, the verifiability principle is not empirically verifiable, though there is speculation that there is an analytic proof possible. Considerable misunderstanding exists as to the thought that the principle invalidates itself since some formulations of the theory do not mention analytic verifiability. It is not clear and was never defined, what exactlöy verification means. It may mean proof, or something weaker, like confirmation. To clear this later "verfifiability" was replaced by "confirmation". Confirmation as a criteria can also be found as the weak verifiabiluity criteria.
Proponents
Hume in many ways was a forerunner of the verification principle; he argued that all meaningful concepts depended on sense experience and/or basic "relations among ideas" ( logical relations mostly), if something could not be traced back to these then it was meaningless.
The classification terms analytic/synthetic have fallen into disuse in contemporary formal logic, but the idea of a statement being empirically verifiable was taken up by in the twentieth century by the logical positivists of the Vienna Circle (the so-called verificationists), who used it to build upon the theory of language that Ludwig Wittgenstein had introduced in his Tractatus Logico-Philosophicus. In essence, the positivists equated Kant's synthetic statements with empirical statements. If an empirical statement is true, it ought to be empirically verifiable, and if an empirical statement is false, it ought to be empirically falsifiable. But, the verifiability priniciple is indeed an example of one of Kant's analytic statements. The verifiability theory of meaning is also closely related to the correspondence theory of truth.
The verifiability theory features as an assumption of an important argument for non-cognitivism.