Tractatus Logico-Philosophicus
Russell became an advocate of logical atomism. Wittgenstein developed a comprehensive system of logical atomism in his "Tractatus Logico-Philosophicus" (, 1921). He thereby argued that the universe is the totality of actual states of affairs and that these states of affairs can be expressed by the language of first-order predicate logic. Thus a "picture" of the universe can be construed by expressing facts in the form of atomic propositions and linking them using logical operators.