AJ Ayer was a British philosopher born in 1910. He was educated at Eton, and finished his book 'Language, Truth and Logic' by the age of 25.
He is most famous as an advocate of logical positivism, the theory that metaphysics and statements about religion and morality cannot be verified and are therefore meaningless. The biggest criticism of this theory is that it cannot be verified and is therefore, by its own reasoning, meaningless. Ayer was an atheist.
For more information about AJ Ayer, read Ben Rogers' 'AJ Ayer, A Life', including the story about how 77 year old Ayer picked a fight with Mike Tyson, heavyweight champion of the world - and won.
Ayer died in 1989.
GE Moore was a British philosopher born in London in 1873. He was tutored at home and later a nearby day school, where his excellence in classical studies earned him a scholarship to Trinity College, Cambridge, where Bertrand Russell introduced him to philosophy. Along with Wittgenstein and Russell, he was a founder of the analytic tradition in philosophy. He is best known for his refutation of naturalism - the naturalistic fallacy - which says that you cannot learn moral truths by studying the world, as you cannot move from is to ought (i.e. you cannot move from a statement about the way the world is to a statement about the way the world should be).
After retiring, Moore spent a number of years lecturing in America. He died in Cambridge in 1958.
RM Hare was a British philosopher born in Somerset in 1919. He was educated at Rugby and went on to study at Balliol College Oxford. Although a pacifist, he volunteered for the Royal Artillery and was taken as a POW by the Japanese in 1942.
After the war, he returned to lecture at Oxford, married and had four children. He moved to Florida in 1983 where he held a post as a professor of philosophy until 1994.
Hare died near Oxford in 2002 after a series of strokes.