There appears to be a rhythm in the history of philosophy. Periods of great metaphysical system building are followed by brief periods of antimetaphysical reaction. The great constructive systems of seventeenth-and early eighteenth-century metaphysics were followed by Hume's damnation and Kant's drastic restriction of metaphysics (even though we rightly deem both to have elaborated metaphysical systems). The early nineteenth century saw the revival of grand systematic metaphysics among the post-Kantian German Idealists, only to be followed by the destructive reaction of nineteenth-century positivism. But this too was a passing phase, followed by such metaphysical system builders as Bergson, Bradley, McTaggart, Alexander, and Heidegger. And this again bred a reaction in the inter-war years.
The Manifesto of the Vienna Circle, a pamphlet entitled 'The Scientific World Conception', published in 1929, declared that metaphysical assertions are not false propositions, but nonsensical pseudo-propositions. All true or false propositions are either analytic or empirical. The former yield no knowledge of matters of fact. The latter are the totality of cognitively significant propositions. These have a meaning in as much as they are verifiable in experience. Metaphysical assertions are not analytic, for they are not true in virtue of the meanings of their constituent terms, are not derivable from the laws of logic and explicit definitions alone, and do not express conventions for the use of terms (these alternative formulations surprisingly being taken to be roughly equivalent). But they are not empirical propositions either, for they are not verifiable in experience, they have no determinable truth-conditions, and make no difference to any possible experience (these formulations being similarly taken to be equivalent).
The argument was essentially a rerun of Hume's condemnation of