Early criticsEarly critics of logical empiricism said that its fundamental tenets could not themselves be formulated in a way that was clearly consistent.
The verifiability norm of meaning did not seem verifiable; but neither was it simply a logical tautology, since it had implications for the practice of science and the empirical truth of other statements.
This presented severe problems for the logical consistency of the theory said opponents.
Norms can be good or bad and different norms can be contradictory.
Universal claims could apparently never be verified: How can you tell that all ravens are black, unless you've hunted down every raven, including those in the past and future? This led to a great deal of work on induction, probability, and "confirmation," which combined verification and falsification.
Logical empiricists' response to the first criticism was that logical empiricism is a philosophy of science, not an axiomatic system that can prove its own consistency (see Gödel's incompleteness theorem). Secondly, a theory of language and mathematical logic were created to answer what it really means to make statements like "all ravens are black."
Many commentators on logical empiricism have attributed to its proponents a greater unity of purpose and creed than they actually shared, overlooking the complex disagreements among the logical empiricists themselves.
Because the principle of verification is a human norm we have no need to to require that it is necessary to use this norm to such propositions which are impossible to verify because we can not make infinite number of observations.
Popper thought that falsifiability was a better norm because it did not invite the philosophical problems inherent in verifying an induction, and it allowed statements from the physical sciences which seemed scientific but which did not meet the verification norm.
Popper's concern was not with distinguishing meaningful from meaningless statements, but distinguishing scientific from metaphysical statements.
Unlike the positivists, he did not hold that metaphysical statements must be meaningless; he also held that a statement which was "metaphysical" and unfalsifiable in one century (like the ancient Greek philosophy about atoms) could, in another century, be developed into falsifiable theories that have the metaphysical views as a consequence, and thus become scientific.
Popper denied that science need rely on inductive reasoning, or that inductive reasoning actually exists, although most philosophers think it obvious that science does rely on it.
"A proposition is said to be verifiable, in the strong sense of the term, if, and only if, its truth could be conclusively established by experience." (Ayer 1946:50)
It is this sense of verifiable that causes the problem of verification with negative existential claims and positive universal claims.
However, the weak sense of verification states that a proposition is "verifiable... if it is possible for experience to render it probable" (ibid.).
After establishing this distinction, Ayer goes on to claim that "no proposition, other than a tautology, can possibly be anything more than a probable hypothesis" (Ayer 1946:51), and therefore can only be subject to weak verification.
This defense was controversial among logical positivists, some of whom stuck to strong verification, and claimed that general propositions were indeed nonsense.
Weak verification is necessary if we know that the set is infinite or it is impossible for man to observe all elements of the set.
The "received view" operates on the correspondence rule that states "The observational terms are taken as referring to specified phenomena or phenomenal properties, and the only interpretation given to the theoretical terms is their explicit definition provided by the correspondence rules."
Putnam argues that introducing this dichotomy of observational terms and theoretical terms is the problem to start from. Putnam demonstrates this with four objections:
If we subtititute "raw data" for "observations" we have no problems.
My opinion is that the word "theory" is unnessesary and emotional.
W. V. O. Quine criticized the distinction between analytic and synthetic statements and the reduction of meaningful statements to immediate experience.
Work by Thomas Kuhn has claimed that it is not possible to provide truth conditions for science independent of its historical paradigm.
This criticism was not unknown to the logical positivists: Otto Neurath compared science to a boat which we must rebuild on the open sea.
My opinion is that we should not use the word "true" for "sentences" of formal languages. We should use the word true only for empirical propositions.
"Meaning" is not a necessary word. The norms of the logical empiricism will not need the word "meaning".
Other scientists have refuted Kunhn's doctrine of paradigms (some of the are Finn scientists).
And later, it was brought to American universities by members of the Vienna Circle after they fled Europe and settled in the United States during and after WWII.
Logical positivism was influential philosophy of science between World War I and the Cold War.
John Passmore said that, that logical empiricism is "dead, or as dead as a philosophical movement ever becomes."
By the late 1970s A. J. Ayer said in a interview: "I suppose the most important [defect]...was that nearly all of it was false."
Perhaps logical empiricism is dead for most philosophers but it lives in the strict sciences. No one has disproved logical empiricism because it is not falsibiable. The definitions and the norms are not falsifiable.