Logical positivism

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Logical Positivism

Also known as logical empiricism

What is logical and what is positive in Logical Positivism?

Logical positivism is a marriage between empiricism and a version of rationalism. Logical Positivism combines the idea that observational evidence is indispensable for knowledge of the world with mathematical and logico-linguistic constructs and deductions in epistemology.




Wrote the book 'Tractatus Logico-philosophicus' which is a set of statements, e.g. a statement is either true or false which is influenced by the belief in power of language for language represents reality. Wittgenstein in this book says that - statement is an atom of a language - statements are beliefs - world is made of facts that corresponds to statements - relationship between things make the world meaningful

He states metaphysics to be meaningless where, as per Wittgenstein's criterion, the idea of meaning is that "all knowledge should be codifiable in a single standard language of science".

Vienna Circle


say that metaphysics, poetry are meaningless whatever is not verifiable is meaningless






A J Ayer

Sir Alfred Jules Ayer (29 October 1910, London – 27 June 1989, London), also known as Freddie was a British philosopher who is well known for his pursuits in logical positivism in developing and spreading it further. He wrote the very famous book of his Language, Truth, and Logic when he was just 26, in which he put forward an emotivist theory of ethics. Setting out the distinction between "strong" and "weak" verification in this book, he states that no proposition, other than a tautology, can possibly be anything more than a probable hypothesis. Ayer sought further major theses of logical positivism, rejection of possibility of synthetic-a priori knowledge and meta-ethical emotivism. He defines the method of Philosophy to be the analysis of the meaning of key terms like ‘causality’, ‘truth’, ‘knowledge’, ‘freedom’, etc. Ayer talks about ontology, the theory of being in itself, and cosmology, the theory describing the origin and structure of the universe in terms of phenomena not commonly experienced by senses. He proposes philosophy to be genuine branch of knowledge, distinct from metaphysics

He was inspired strongly by

         o Russell's essays
         o G.E. Moore's Principia Ethica
         o Philosophical experience he got in Vienna being a member of the Vienna Circle
         o Wittgenstein's Tractatus

The very first chapter of this book talks about the elimination of Metaphysics which he does by asking for valid process of reasoning the very "conception of transcendence". By assuming the metaphysics to be making sense he derives inferences from it. The inferences he obtains seem baseless that are though, drawn from the premise that 'metaphysics is true'. This way he concludes metaphysics to be senseless.

Ayer denies the role of intellectual intuition in knowing facts that can't be known with senses/experience for accepting it seems to be logically unjustified. Being logical positivist, he supports the criterion of verifiability to test whether a sentence/question is significant. He, in his book, describes a 'meaningful sentence' to be either empirical/verifiable (that needs empirical verification to know its truth/falsehood) e.g. cells undergo apoptosis; or the sentence to be tautologous/analytical needing no verification forsuch sentences are necessarily true, true by definition, and true under any conditions, e.g. A is not equal to not A.

In describing the criterion of verifiability, he says that a question is valid when one is able to answer it on the basis of an observation, while a sentence is factual if and only if it is known how to verify the proposition it expresses. He further defines verifiability to be of two kinds a. verifiability in practice (which is when verification is possible in the contemporary conditions) and b. verifiability in principle (which is when some propositions can't be practically verified due to inability to do so, e.g. there are mountains on the farther side of the moon). The verifiability in principle is theoretically possible.

He also takes further this criterion of verifiability further stating two kinds of senses to it. 1. Strong sense, that asks the question - "would any observation make a statement's truth/falsehood, logically certain...?" 2. Weak sense, that asks the question - "would any observation be relevant to the determination of a statement's truth/falsegood...?" Thus, in the weak sense of the criterion of verifiability, Ayer seems to have made the criterion a more flexible one, which of course later arose the difficulties in sustenance of the very logical positivism itself.

Ayer, in his book 'Language, Truth, and Logic' criticizes metaphysicians' statements for not being verifiable even in principle and having no observational ground, e.g. 'The absolute enters into, but itself is incapable of, evolution and progress'. He very strongly calls them to be insignificant and nonsense statement that have superficial gramatical feature. Ayer also comments on the debate between realists and idealists giving the example of a situation where both realists and idealists analyze Goya's picture. He supports the idea that existance is not an attirbute and thus statements with existance as an attribute are senseless, e.g. Unicorns are fictitious. He says that in fact attributing something implies its very existance.


is a consequentialist


Karl Popper

               + introduces
                     # falsifiability
                     # no empirical content in his epistemology
   * Hypthetico-deductive model (HD)
         o states that
               + with theory, hypotheses and facts/observations, propositions can be deduced
                     # which gives out
                           * verifiability
                           * meaning
                                 o e.g. concepts have meaning but no truth value
                           * truth to the theory
   * says that
         o truth comes from verification
   * states two kinds of statements which are
         o General statements
               + are
                     # not verifiable
                     # assumed to be true
                     # deduced the consequences from
         o Particular statements
               + are
                     # verifiable through experience
   * also give another kind of statements
         o normative
         o descriptive
               + e.g. phenomena description
   * states that philosophy has
         o values
               + that are
                     # meaning
                     # truth
                     # validity