Logical positivism

Logical Positivism was a philosophical school originating in Vienna in the early years of the Twentieth century. The originators of the philosophy are often referred to as the "Vienna Circle". The Circle's views were first brought to the attention of the English speaking world by A. J. Ayer in his work "Language, Truth and Logic".

Logical Positivism sought to eliminate metaphysics from philosophy to which end it proposed a criterion of verifiability:

"a sentence is facually significant to any given person, if, and only if, he knows what observations would lead him , under certain conditions , to accept the proposition as being true, or accept it as being false." ( A. J. Ayer, "Language, Truth and Logic" Second Edition, Victor Gollancz Ltd, 1946 page 35).

That is to say that if there is no empirical evidence, for or against, the propostion fails to have any meaning: it is simply nonsense.