The recent downsizing of A.J. ('Freddie') Ayer is none too soon. For several decades no one who went to Oxford could escape the stultifying influence of his Logical Positivism and its associated Verification Principle - the view that, apart from logic and mathematics, all statements which cannot be verified empirically are meaningless.
This doctrine managed to be both trivialising and nihilistic. Trivialising, because it dismissed all the traditional problems of philosophy as 'pseudo-problems' arising from a misuse of language. And nihilistic, because it consigned the whole of human thought outside the natural sciences to a limbo of personal opinion ('emotivism') on which nothing true or false could be said.
Far from remaining, as it deserved to, an amusing game, logical positivism infected the study of all humane subjects. It turned social studies into social 'sciences', aping the methods of the natural sciences in an attempt to say something 'meaningful'. And the reaction against this led to Continental post-structuralism, which sees all social discourse as paradox and self-delusion. Intellectual life is only now recovering from this double assault. To cap it all, Ayer did not even understand the methods of the natural sciences.
Ayer did not originate logical positivism, he popularised it. His success was due to a lucidity which now seems merely hyonotic and to a personality and lifestyle which distance has robbed of most of their charm.