The union of logic and empiricism was solemnized in the first really independent philosophical writings of the first man to combine the requisite logical and philosophical expertise, in Our Knowledge of the External World (1914) and Philosophy of Logical Atomism (1918) of Bertrand Russell. ... Wittgenstein's Tractatus Logico-Philosophicus (1922) was the first brilliant wayward child of the marriage, but the parental lineaments were more obvious in the logical positivism of the Vienna Circle.