A J Ayer – Logical Positivism
Seminal work: Language, Truth and Logic
This was published when he was 26.
He was the most outspoken proponent of Logical Positivism.
Attended Eton and was fairly precocious.
Scholarship to Christ Church, Oxford to study classics.
Had four wives one of which was Vanessa Salmon, he was therefore
stepfather to Nigella Lawson.
Supported Spurs keenly.
Described as charming but intimidating.
Central Axiom
The Verification Principle:
“non-tautologous statements are meaningful only if it is in principle possible
to establish empirically whether they are true or false”
An unmarried man is a bachelor. ->Tautologous statement. Analytical.
Mathematics is analytical also according to Ayer, any proposition of
mathematics contains every other truth it is only our intellectual limits
which result in surprise and a process of discovery.
There is cake at philosophy society. -> Non-tautologous. Synthetic.
There truth value (1 or 0) of these statements is not implied within the
statement, “you must go out into the world to discover the truth”
N.Gardiner.
Strong Verificationism - largely rejects generalisations such as all swans are
white, on the grounds that an infinite number of swans (all time periods)
would have to be observed to verify this claim.
Whereas…
Weak Verificationism – believe it need only be probable that the
generalisation is true based on a finite amount of empirical evidence
Logical Positivism does not propose that propositions that cannot be
verified are false but literally that they are meaningless. Asserting that
such a proposition is true or false is a waste of time.
What subjects are therefore meaningless?
God – Ayer dissociated himself from atheism, agnosticism and belief in God
because he argued propositions concerning a being who was by definition
ineffable were clearly meaningless.
Metaphysics – That philosophy affords us knowledge of a transcendent
reality is meaningless, metaphysicians are abusing the laws of
significant language. (Kant had similar ideas though suggested we were
merely unable to make propositions on a transcendent reality because
of the limits of human understanding.)
Ethics – Kinda.
The death of Ethics. 
Ayer broke ethical philosophy into 4 kinds of statements:
-> "Propositions that express definitions of ethical terms, or judgements
about the legitimacy or possibility of certain definitions”: basically
defining words and their interrelation, this is the analytical work that
Ayer believes is all philosophers should be doing, purely critical.
-> "Propositions describing the phenomena of moral experience, and
their causes”: feelings and mental reactions to situations and actions
related to ethics and morals e.g. rape/being compelled to defend victim.
Ayer deems this the realm of the psychologist.
-> "Exhortations to moral virtue”: rhetorical statements of moral
preference “you shouldn’t do that”. Ayer calls these “ejaculations…to
provoke the reader”. Oration, linguistics etc.
-> "Actual ethical judgments”: e.g. you should save the man in the
nearest burning house. These are the result of reasoning within an
ethical system which requires only sound knowledge of the system and
the mechanics of it’s logic. Things like, what would bring the most utility,
what would conform to evolutionary development?
Logical positivism therefore moved analytical philosophers towards
emotivism also referred to as the “Boo, Hurrah!” theory.
But don’t worry, ethics isn’t dead, Rawls and GEM Anscombe released
works of deontology and virtue ethics respectively which are posed less
risk by LP. Furthermore utilitarianism never really dies, after all it is
somewhat similar to emotivism.
Problems with Logical Positivism
-> The proposition, or rather complex interrelation of situations that is LP can
themselves not be verified. Under what circumstance could empirical
evidence validate LP? Ayer suggests vaguely that it’s success (i.e. that it is
useful and productive using LP) is evidence to commend it. However this is
to presuppose that induction as the keystone in the empirical process is
logically sound which it is not.
-> Quine believed that synthetic and analytical propositions can not easily be
separated. Also every assertion relies upon a multitude of pre-established
knowledge which must be verified in accordance with the ad-hoc
proposition, this is hard.
-> Popper condemned LP for affirming the consequent a common mistake in
logic and a rhetorical device used to convince simpletons.
antecedent
consequent
If H then P
P therefore H
“Confirming the antecedent”, “converse error”.
If all balls bounce when dropped from a height, then, this ball will
bounce when dropped from a height.
This ball bounced when dropped from a height, therefore, all balls
will bounce when dropped from a height.
(Asserting “P” means “p is true”. P has a truth value of 1
in this propositional logic.)
To give scientists something useful to do that wasn’t logically destroyed
Popper came up with falsificationism. We may not be able to prove the
general from the specific but we can disprove the specific from the
general.
If H then P
Not P therefore not H
Scientists should spend their time trying to disprove hypothesis.