Logical Positivism – Ayer

In a series of articles I will be forming a bite size guide to the philosophical composition known as Logical Positivism.


Logical positivism was a school of thought that appeared in Vienna in the 1920’s. It was centred around the discussions of a group of philosophers known as the Vienna Circle. They discussed logic, mathematics, language and had a great distaste of metaphysics. They claimed that true knowledge was gained through sense experience and reason alone. Influenced by advances in modern science, logical positivists sought to apply the scientific paradigm to philosophy and show metaphysics to be meaningless.


A.J.Ayer was a British philosopher best known for his books ‘Language, Truth and Logic’ and ‘The Problem of Knowledge’. He was born in London on October 29th, 1910 and died on 27th June 1989 from a collapsed. He lectured at University College London and at Oxford University. Hes was knighted in 1970.


  At the foundation of Ayer’s approach to logical positivism is his complete rejection of metaphysics. By investigating Ayer’s arguments against metaphysics we can learn more of his preference of empiricism and hence of logical positivism.

  Ayer completely rejected metaphysics in his book ‘Language, Truth and Logic’. Ayer claims that any proposition a metaphysician makes must originate from evidence from their senses and then suggests an inability to derive a conclusion which claims to be transcendent of empirical knowledge from an initial empirical premise. In reply to this criticism of metaphysics one could simply deny that the initial premise was based on sense experience. Or, even if they were to accept that the initial premise was based on sense experience and that it is not logical to move from this to a metaphysical conclusion, it does not mean the statements that seem to surpass the sensory world could not be true. So Ayer’s goes on to criticise the actual metaphysical statements themselves.  He says that no metaphysical statement which ‘transcends the limits of all possible sense experience can possibly have any literal significance’. So, even if we can imagine such metaphysical statements they can’t relate to anything true. Ayer’s rejection of metaphysics and support of empiricism is key to his formulation of the Verification Principle as mentioned later on.

Language, Truth and Logic

It is Ayer’s support of not only empiricism but rationalism also that makes his beliefs that of a logical positivist and not just any other empiricist. Ayer highlights that it may appear that empiricism and rationalism are incompatible as empiricism maintains that all knowledge comes from sensory experience which seems to contradict the rationalist’s idea of a knowledge of necessary and logical truths, such as mathematics. He also suggests that if a proposition relies on sensory experience to be valid it can never logically be certain as sensory experience can change over time. This implies that one would have to choose between empiricism and rationalism but Ayer finds a way to marry to two philosophical thoughts by accepting that necessary truths exist but claiming that they haver no ‘factual content’. Ayer maintains that ‘all of our knowledge begins with experience but that does not mean it all arises from experience’. So, all of our knowledge of maths begins with learning maths but the maths itself does not come from experience but some logical necessary truths.

It may be questioned how necessary truths can still be valid if they do not adhere to the requirements of empiricism that they be based on sensory experience. This is where Ayer distinguishes between analytic and synthetic statements, both of which are valid, but analytic statements involve the ‘proposition’s validity being dependent on the definitions of the symbols it contains’, and the validity of synthetic statements being ‘determined by facts of experience’ It is the combination of an empiricist and rationalist approach that produces the logical positivist school of thought.


Ayer’s main contribution to the logical positivist school of thought was the Verification Principle. It seems that a basis for Ayer’s philosophical thought was greatly influenced by Bertrand Russell’s thought in his ‘Sceptical Essays’ that propositions should have reasons to believe them which is reflected in the Verification Principle. The Verification Principle is the claim that a sentence is factually significant if and only if a person knows how to prove or disprove the proposition. So, empirical statements comply with the Verification Principle as they can be verified through sensory experience. Rational statements such as logic and maths also adhere to the Verification Principle as they can be verified through the analysis of the definitions that the statement contains. Through Ayer proposing the Verification Principle he enables the simultaneous acceptance of both empiricism and rationalism as they both adhere to the principle, which is exactly what logical positivism is.