Logical Positivism – Philosophy Notes

Logical Positivism philosophy of logical positivism originated from Wittgenstein’s statement in the tractatus that “philosophy is not a theory but an activity.” This movement was started by a group of thinkers known as the Vienna Circle who lived in Vienna during the 1920s. The rejection of metaphysics had its roots in the philosophy of Hume and Kant, but it was the logical positivists who actively opposed metaphysics. This trend had two main aspects:

Firstly, it aimed to establish the foundation of science by eliminating pseudo-concepts of metaphysics and basing it on strictly empirical principles.

Secondly, it aimed to discredit traditional philosophies, proving their futility and condemning metaphysics as meaningless, invalid and misleading.

Logical positivists hold that speculation about that which transcends experience is a waste of time and energy as it has no meaning or sense. Theories and principles that are relevant are those that concern something within our experience and can be verified or falsified based on empirical facts. Metaphysical theories are not based on experience and are therefore considered meaningless. Although they are non-experiential, they are not considered foolish or folly.

The role of philosophy, according to this school of thought, is to analyze scientific statements and examine their types and relationships. Herbert Feigl’s witty remark about philosophy exemplifies this outlook: “Philosophy is the disease for which it should be the cure.”

Philosophy serves as grammar to science, providing rules for determining the correctness of scientific assertions, similar to how grammar provides rules for language.

The Verification Principle & Elimination of Metaphysics

The logical positivist’s attack on traditional philosophical systems, such as logical atomism, was based on two fundamental principles: the distinction between “analytic” and “syntheticpropositions and the criterion for determining cognitive meaningfulness, known as the “verification principle.” To comprehend this attack, it is crucial to understand these principles.

The distinction between “analytic” and “synthetic” propositions is illustrated by the following two propositions:

(a) All husbands have a head, and

(b) All husbands are married.

While both propositions are true, they differ in the way they are true.

Proposition (a) is true because no husband exists without a head. However, it is possible to imagine a man born without a head, who lives, is fed through tubes, marries, and becomes a husband.

Proposition (b) is not just true in fact; it is impossible to imagine any circumstances in which someone could be a husband without being married. This distinction shows that propositions requiring empirical investigation for confirmation are synthetic, while those whose truth follows from their meaning are analytic.

Logical positivists believed that all significant propositions must be either analytic or synthetic, but not both. Analytic propositions are true due to their formal structure, and synthetic propositions are like those of science, requiring empirical investigation for their validation. They also believed in the verification principle, which stated that a proposition is cognitively meaningful if and only if it can be confirmed or disconfirmed through empirical observation or logical analysis. This principle led to the elimination of metaphysics since metaphysical propositions are not based on empirical evidence and cannot be verified, making them meaningless.

To put it in other words, analytic propositions derive their name from the fact that the predicate is inherent in the definition of the subject term. Therefore, these propositions merely state something about the subject that is obtained by analyzing the subject term. For example, “All husbands (i.e., married males) are married.” To confirm the validity of such propositions, one must analyze the words used in the statement.

In contrast, synthetic propositions are named so because they join together two logically unrelated things. Hence, they are verified through observation and empirical investigation. For example, “This desk is brown.”

It is important to note that analytic propositions do not refer to the world in the same way as synthetic propositions. The truth of an analytic proposition does not imply the existence of the items mentioned in the statement. On the other hand, the truth of a synthetic proposition suggests that the world contains at least one of the items mentioned in the statement.

Logical positivists categorized analytical propositions as “trivial” and synthetic propositions as “informative.” Analytical propositions are trivial because they do not make any claim about the world upon analysis. Synthetic propositions, on the other hand, are informative because they make claims about reality.

Russell and Whitehead developed mathematical and logical techniques to determine whether a proposition is analytic or not. However, identifying whether a synthetic proposition is significant or not required a different test, which the positivists named the verifiability criterion of meaning.

According to this criterion, a synthetic proposition is significant only if it can be verified empirically. If a proposition fails to pass this test, it may be either analytic or nonsensical. Therefore, any proposition that aims to convey factual knowledge about the world must pass the test of empirical verifiability to be considered significant. For instance, the proposition “God exists in a heavenly place” purports to be about the world, but its significance depends on whether it can be empirically verified.

What is the verifiability criterion?

This criterion has been formulated in various ways by different philosophers. Schlick, in a paper titled “Realism and Positivism,” formulates the principle in at least five different ways. One of its most famous statements can be found in Ayer’s book “Language, Truth, and Logic,” published in 1936. According to Ayer, a sentence will only be factually significant to a person if they know how to verify the proposition that it purports to express. That is, they must know what observations would lead them under certain conditions to accept the proposition as being true or reject it as being false.

The principle’s key term is “observation,” which emphasizes the importance of being able to describe the types of observations that would need to be made to determine whether a proposition is true or false. If a relevant observation can be described, the proposition is significant; if not, it is meaningless. Schlick provides an example to illustrate the principle, where someone asserts that the universe is shrinking uniformly, but no observation can prove it, making the assertion nonsensical.

Schlick claims that philosophical theories that make such assertions are nonsensical. If a philosopher holds a proposition that cannot be verified, Schlick argues that it will be nonsensical because no possible observation can be described to determine its truth or falsity. When explaining the verifiability criterion, it is important to distinguish between propositions that are verified and those that are verifiable, or, in other words, between practical verifiability and verifiability in principle.

For instance, the proposition “There is extraterrestrial life” has never been verified by anyone. Still, it is a verifiable proposition because we can describe the steps we must take to verify it. We must first find some means of reaching other parts of the universe and then look to see if there is life there. If we determine that there is life there, the proposition will be true, and if not, it will be false.

Let us consider, as a contrasting example, the proposition “God exists in a heavenly realm.” What kind of conditions or steps could possibly demonstrate the truth of this proposition? There are no observations we could make that would confirm or refute the proposition, even in principle. To suggest that we could determine the truth of the proposition after we die is simply another way of acknowledging that no relevant observations could be made in the present. Because there is no conceivable way to verify this proposition, it expresses no meaningful idea and is therefore not a cognitively significant statement.


Wittgenstein is often credited with the initiation of logical positivism due to his remark in the Tractatus that philosophy is not a theory but an activity. He believed that philosophy is simply the analysis and discussion of language, which is a symbolic expression of facts of experience. Wittgenstein asserted that the entire fabric of language can be broken down into compound statements, which can in turn be analyzed into simple statements. A simple proposition is a reflection of reality and is true if it corresponds to facts, and false if it does not.

Wittgenstein’s analysis of language implies that every linguistic expression is connected with some fact of experience, either directly or indirectly. Therefore, any linguistic expression that fails to show any connection with any fact is considered a pseudoproposition. For instance, the statement “God exists” is neither true nor false, but rather a pseudoproposition since it does not correspond to any fact of experience.

Wittgenstein believed that metaphysical language is problematic and confusing because it deals with concepts that transcend experience. He argued that these problems arise due to a conscious or unconscious abuse of language. Therefore, the job of philosophy is to eliminate this confusion and show that metaphysical problems are unreal. Wittgenstein rejects metaphysical statements as propositions because they cannot be verified by experience and, thus, must be considered meaningless.

Metaphysicians claim that these statements are based on internal experience, but Wittgenstein does not recognize this. He argues that they cannot be known unless they are expressed and linked to an objective reality, which they cannot be since they are unverifiable. Wittgenstein uses the verification theory to claim that metaphysical statements lack an objective referent and, therefore, are unverifiable.

Rudolph Carnap

Rudolph Carnap rejects metaphysics not because of the lack of an objective referent, as Wittgenstein does, but because metaphysical statements are devoid of meaning or sense when subjected to linguistic analysis.

In order to determine the meaning of an expression, Carnap laid down four criteria that elementary sentences must serve. These include

  • the derivation of elementary sentences and the types of sentences produced by them,
  • the circumstances under which they are true or false,
  • how they can be verified, and
  • what their meaning is.

When these criteria are applied to metaphysical expressions, it is found that they do not satisfy any of them. For instance, the various assertions about God are contradictory and incomprehensible. Assertions such as “all reality is mental” are also meaningless because there is no experience of “all.” Carnap calls such statements “pseudo-concepts” because they are constructed using meaningful words, but the sentence as a whole is meaningless.

Metaphysicians argue that their assertions are not based on the experience of ordinary people, but on the experience of spiritually elevated persons who possess extraordinary powers of intuitive knowledge. According to Carnap, however, no statement can be considered meaningful unless it is fully supported by empirical evidence that can validate or invalidate it. Therefore, he rejects the argument that metaphysical assertions cannot be evaluated by ordinary rational standards because they are based on non-ordinary experiences.

AJ Ayer

A.J. Ayer proposed a distinction between philosophy and metaphysics, arguing that while philosophy and science are closely related, metaphysics has no connection with philosophy. This is because metaphysics deals with realms that have no connection with observable facts, and none of its statements are scientifically verifiable. As a result, metaphysical statements should be rejected as meaningless and senseless.

For instance, the concept of God cannot be empirically verified, and the claim that God can be known through intuition cannot be scientifically verified. Ayer also noted that there is no way to distinguish between intuitive knowledge and hallucination.

Ayer classified existence into two types: empirical, which is experiential through sense organs and therefore verifiable, and transcendental, which is beyond experience and thus not verifiable. He proposed the principle of verification, which states that any statement that is beyond the scope of verification is meaningless and a pseudo-statement.

Ayer classified propositions into three categories based on the principle of verification: 

  • Verifiable,
  • not verifiable but can be verified with suitable apparatus,
  • and impossible to verify.

He further distinguished between strong verifiability, which is practically verifiable, and weak verifiability, which is not directly or practically verifiable but may be possible in the future, such as the existence of life on Mars.

Thus, Ayer believed that a proposition is meaningful if we can discover practical and demonstrable instances. However, he acknowledged that applying such criteria could make many historical and scientific statements meaningless. Therefore, he modified the principle of verifiability to state that a proposition is meaningful only if it is possible, in principle or practice, to have sense perception that can directly or indirectly demonstrate its truth or falsehood or at least its probability.

Critical comments on Logical Positivism

  1. Deprived philosophy of traditional functions, such as being surveyors of knowledge and determiners of what constitutes valid knowledge, and revealing hidden laws of the universe.
  2. Restricted philosophy to a narrow and technical function of evaluating scientific assertions.
  3. Overvalued science and failed to recognize that philosophy is the science of sciences.
  4. The principle of verification is grossly exaggerated. Many beliefs are fundamental to life, but unverifiable. Moreover, the verification principle itself is unverifiable.
  5. Conception of knowledge is too mechanical, as they reject the value and importance of imagination and creativity.
  6. Concepts like God, soul, other-worldliness, etc. have great pragmatic value and provide religious consolation, satisfying the practical interests of man.

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