The Tractatus is written as a series of hierarchical propositions. Most of the book is concerned with expounding Wittgenstein's system of logic, where, among other things, he propositions and the way that propositions relate to states of affairs in the world. In the course of setting out his system, Wittgenstein is able to lay to rest many important problems encountered by Bertrand Russell in the Principia Mathematica.
There is more to Wittgenstein's Tractatus than its logical content, however. Throughout the Tractatus, Wittgenstein is also concerned to spell out what can and cannot be discussed with language. Towards the end of the book, Wittgenstein also considers the ramifications of his theory of language for ethics and metaphysics.
Most scholars divide Wittgenstein's philosophy into its early and late stages. These scholars consider the Tractatus Logico-Philosophicus the definitive summary of Wittgenstein's early philosophy. The Tractatus was also an influential work for the positivist Vienna Circle centered around Moritz Schlick.