---
title: "Logical positivism"
chunk: 2/5
source: "https://en.wikipedia.org/wiki/Logical_positivism"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T03:11:36.284431+00:00"
instance: "kb-cron"
---

=== Anglosphere ===
As the movement's first emissary to the New World, Moritz Schlick visited Stanford University in 1929, yet otherwise remained in Vienna and was murdered in 1936 at the University by a former student, Johann Nelböck, who was reportedly deranged. That year, A. J. Ayer, a British attendee at various Vienna Circle meetings since 1933, published Language, Truth and Logic, which imported logical positivism to the English-speaking world. In 1933, the Nazi Party's rise to power in Germany had triggered flight of intellectuals, which accelerated upon Germany's annexation of Austria in 1938. The logical positivists, many of whom were Jewish, were targeted and continued flight throughout the pre-war period. Their philosophy thus became dominant in the English-speaking world.
By the late 1930s, many in the movement had replaced phenomenalism with Neurath's physicalism, whereby material objects are not reducible to sensory stimuli but exist as publicly observable entities in the real world. Neurath settled in England, where he died in 1945. Carnap, Reichenbach and Hempel settled permanently in America.

=== Post-war period ===
Following the Second World War, logical positivism—now referred to by some as logical empiricism—turned to less radical objectives in the philosophy of science. Led by Carl Hempel, who expounded the covering law model of scientific explanation, the movement became a major underpinning of analytic philosophy in the English-speaking world and its influence extended beyond philosophy into the social sciences. At the same time, the movement drew intensifying scrutiny over its central problems and its doctrines were increasingly criticised, most trenchantly by Willard Van Orman Quine, Norwood Hanson, Karl Popper, Thomas Kuhn and Carl Hempel.

== Principles ==

=== Verification and Confirmation ===

==== Verifiability Criterion of Meaning ====
According to the verifiability criterion of meaning, a statement is cognitively meaningful only if it is either verifiable by empirical observation or is an analytic truth (i.e. true by virtue of its own meaning or its own logical form). Cognitive meaningfulness was defined variably: possessing truth value; or corresponding to a possible state of affairs; or intelligible or understandable as are scientific statements. Other types of meaning—for instance, emotive, expressive or figurative—were dismissed from further review.
Metaphysics, theology, as well as much of ethics and aesthetics failed this criterion, and so were found cognitively meaningless and only emotively meaningful (though, notably, Schlick considered ethical and aesthetic statements cognitively meaningful). Ethics and aesthetics were considered subjective preferences, while theology and metaphysics contained "pseudostatements" that were neither true nor false. Thus, logical positivism indirectly asserted Hume's law, the principle that factual statements cannot justify evaluative statements, and that the two are separated by an unbridgeable gap. A. J. Ayer's Language, Truth and Logic (1936) presented an extreme version of this principle—the boo/hooray doctrine—whereby all evaluative judgments are merely emotional reactions.

==== Revisions to the criterion ====
Logical positivists in the Vienna Circle recognised quickly that the verifiability criterion was too restrictive. Specifically, universal statements were noted to be empirically unverifiable, rendering vital domains of science and reason, such as scientific hypothesis, cognitively meaningless under verificationism. This would pose significant problems for the logical positivist program, absent revisions to its criterion of meaning.
In his 1936 and 1937 papers, Testability and Meaning, Carnap proposed confirmation in place of verification, determining that, though universal laws cannot be verified, they can be confirmed. Carnap employed abundant logical and mathematical tools to research an inductive logic that would account for probability according to degrees of confirmation. However, he was never able to formulate a model. In Carnap's inductive logic, a universal law's degree of confirmation was always zero. The formulation of what eventually came to be called the "criterion of cognitive significance", stemming from this research, took three decades (Hempel 1950, Carnap 1956, Carnap 1961). Carl Hempel, who became a prominent critic of the logical positivist movement, elucidated the paradox of confirmation.
In his 1936 book, Language, Truth and Logic, A. J. Ayer distinguished strong and weak verification. He stipulated that, "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", but is verifiable in the weak sense "if it is possible for experience to render it probable". He would add that, "no proposition, other than a tautology, can possibly be anything more than a probable hypothesis". Thus, he would conclude that all are open to weak verification.

=== Analytic-synthetic distinction ===