Ludwig Wittgenstein wrote the Tractatus Logico Philosophicus as a tightly argued, aphoristic account of the relation between language, thought, and reality. The work is presented as a sequence of numbered propositions that build from the most basic observations to far reaching conclusions about what can meaningfully be said. At the center of Wittgenstein’s project is the idea that language pictures the world. A meaningful proposition is one that represents a possible state of affairs by sharing a logical form with that state of affairs. In this picture theory a proposition is like a model or map whose elements correspond to objects and whose structure mirrors how those objects might be arranged in reality.
Wittgenstein begins by identifying the world as the totality of facts, not of things. Facts are structured combinations of objects, and the simplest constituents are what he sometimes calls simple objects. Propositions are meaningful insofar as they are pictures of these facts. To show this, he develops an account of logical form. Logical form is what a proposition must have in common with the reality it pictures; it cannot itself be put into words without presupposing that very form. That leads to an important distinction in the book between what can be said and what can only be shown. Many essential features of reality and language are shown in the structure of propositions and in logical grammar, but they are not themselves propositions that can be asserted.
From the picture theory Wittgenstein draws consequences about the limits of language. Propositions about contingent states of affairs can be true or false depending on whether the pictured arrangement obtains. Propositions of logic and mathematics, by contrast, do not picture possible states of affairs in the same way; they are tautologies. As tautologies they cease to tell us anything about the world; they only make explicit the scaffolding of thought. Ethics, aesthetics, and much of metaphysics occupy the same borderline region. They are deeply important, yet they resist being captured in propositional language. Wittgenstein insists that attempts to say the mystical, the ethical, or the ultimate meaning of life run up against the limits of what can be expressed.
A recurring claim is that philosophy is not a doctrine but an activity that clarifies thought by exposing confusions in our language. Philosophy should show the skeleton of thought and language, dissolving pseudo problems that arise when language is misused. Hence many of the book’s propositions are corrective. Wittgenstein aims to delineate clearly the boundary between sense and nonsense, between propositions that picture the world and expressions that fall outside the realm of literal saying. He treats much traditional metaphysical theorizing as nonsensical in the special, technical sense that it attempts to say what can only ever be shown.
The Tractatus is also notable for its austere, even ascetic, tone. Wittgenstein moves from logic and language to the question of how one should live with the realization of language’s limits. He suggests that once the proper boundaries of sense are set, what remains as truly significant is not expressible in factual language. That insight culminates in the book’s famous closing injunction about silence. It is not a renunciation of meaning but an insistence that the deepest truths about value, meaning, and the mystical are not matters for factual assertion.
Historically the Tractatus had a profound influence on early analytic philosophy, especially the logical positivists who adopted a criterion of meaning shaped by Wittgenstein’s emphasis on verification and the structure of language. In time Wittgenstein came to reject and revise many of the positions in this work, leading to a very different view of language in his later writings. Still, the Tractatus remains a striking and original effort to show how language and world hang together, and to map the frontier where speech gives out and silence begins.
Read as a whole the Tractatus is an intellectual journey from concrete logic to the shadowy border of the unsayable, and it leaves the reader with a twin sense of clarity about how language functions and humility about the questions that lie beyond its reach. As Wittgenstein himself puts it, Whereof one cannot speak, thereof one must be silent.