Twentieth-century philosophical movement that used a strict principle of verifiability to reject as meaningless the non-empirical statements of metaphysics, theology, and ethics. Under the influence of Hume, Russell, and the early Wittgenstein, the logical positivists regarded as meaningful only statements reporting empirical observations, taken together with the tautologies of logic and mathematics. Prominent logical positivists included members of the Vienna Circle and Ayer.

(http://www.philosophypages.com/dy/l5.htm#logp)