VERIFICATION
Logical Positivism
Wittgenstein’s formulation, (“To understand a proposition means to know what is the case if the proposition is true.”) suggests that, to understand, is to tell whether there is truth or not.
To understand also means to know how to check the proposition against the conditions under which that proposition might be true – “The street is wet” involves knowing what is it we need to do in order to verify whether the street is wet (looking through the window, going outside, etc.)
Logical Positivism is the view that the very meaning of a proposition depends on whether a proposition can be verified.
To understand a proposition, according to this view, is to know how to verify it – what sort of observations must be made to confirm a proposition to some significant degree.
The verification need only be available in principle and need not be conclusive Ex: I can’t confirm that there are mountains on the other side of the moon by simply looking through the telescope, but the proposition “There are mountains on the other side of the moon” is still meaningful since it is verifiable(all I need to do is go to the other side of the moon and look).
Some radical versions of Logical Positivism go a step further, stating that verification is the meaning of a proposition. The meaning is thus translated into a list of observations we can make, implying a sort of dictionary in which various experiences are matched against propositions.
This extreme step was motivated by the fact that the vocabulary of science contains many terms whose meaning cannot be derived directly from the verification principle and can only be related to certain measurements: What is blood pressure? The meaning of the term “blood pressure” refers us to the set of observations we can make as we learn how to take blood pressure using appropriate tools.
Behaviourism is another example of this approach: Propositions about mental states (especially mental states of others) are meaningful since they are verifiable through observation of certain behaviours: “Smith is angry” can be verified by observing Smith stomping his feet, pounding his fist on the table, yelling, etc.
Logical Positivists considered all non-verifiable propositions meaningless, calling them “pseudo-propositions”, or, less generously – nonsense.
This “nonsense” included most propositions of philosophy, especially metaphysics and, very significantly, moral propositions.
There were many problems with Logical Positivism (mainly concerned with logic and need for ever increasing concessions to metaphysics) that eventually rendered it obsolete.
The “fatal flaw” of Logical Positivism, however, resides in its central view: the verification theory of meaning: The verification principle (in its strong version) states that a non-tautological statement has meaning if and only if it is empirically verifiable.
But the statement of the principle itself is non-tautological yet it cannot be verified empirically, by any sort of observation. By its own definition, therefore, the verification principle renders itself meaningless.