1. Verification and meaning

2. The Vienna Circle Religious Language is meaningless Early 1900s
Founded 1907 by Otto Neurath, Hans Hahn, Philip Frank
1922 – Moritz Schlick leader
Interested in Frege, Russell and Whitehead’s developments in logic
Wittgenstein also important to them

3. Logical Positivism A J Ayer brought their work to English public
‘Language, Truth and Logic’ in 1936
Logical positivism a reaction to 19th century theories of the philosopher Hegel
Hegelianism dominated thought at the time
Emphasis on progress - everything forms part of a spiritual reality called the Absolute
Logical positivists worried that this was a philosophical attempt to state what the universe was like
They thought this was a job for scientists

4. Logical positivism Offers no world-view of its own
Argued that it was no business of the philosopher to say anything at all about the world
The job of philosophy is simply to analyse the logical structure of sentences
They sort them out into meaningful and meaningless statements – the scientist can look into the meaningful ones more

5. Criteria of meaning
The criterion to demarcate a meaningful from a non-meaningful statement:
“The meaning of a proposition is the method of its verification” (Schlick)
This means in practice that there are two types of meaningful propositions:
1. Tautologies.
2. Empirically verifiable propositions.

6. Tautology and empirically verifiable
2+2=4
Bachelors are unmarried males
(true by definition)
Empirically verifiable – must be observable or must entail an observation at some point, directly or indirectly
Eg. Henry VIII had 6 wives – indirectly verifiable through sources

7. Verifiable propositions
Empirical propositions, assert or deny something about the real world
Propositions assert or deny something and may be true or false
In either case they are meaningful
Statements that are not meaningful cannot be expressed as propositions

8. Language, Truth and Logic, A J Ayer
Ayer distinguishes between ‘strong’ and ‘weak’ verification, noting that there is a limit to how conclusively a proposition can be verified
‘Strong’ (conclusive) verification is not possible for any empirical proposition, because the validity of any proposition always depends upon further experience.
‘Weak’ (probable) verification, on the other hand, is possible for any empirical proposition.

9. Practical and theoretical verifiability
Ayer also distinguishes between practical and theoretical verifiability.
Propositions for which we do not have a practical means of verification may still be meaningful if we can verify them in principle
Eg. ‘there are mountains on the far side of the moon’

10. Hume’s influence on the Positivists
Ayer agrees with Hume that there are two main classes of propositions:
those that concern 'relations of ideas,'
and those that concern 'matters of fact.'
Propositions about 'relations of ideas' include the a priori propositions of logic and mathematics.
Propositions about 'matters of fact' make assertions about the empirical world

11. Hume and metaphysics
If we take in our hand any volume; of divinity or school metaphysics, for instance; let us ask, Does it contain any abstract reasoning concerning quantity or number? No. Does it contain any experimental reasoning concerning matter of fact and existence? No. Commit it then to the flames: for it can contain nothing but sophistry and illusion.
— David Hume, An Enquiry Concerning Human Understanding