Book: Tractatus Logico-Philosophicus

Overview
Tractatus Logico-Philosophicus is a compact, aphoristic attempt to map the limits of language and, by doing so, to delimit what can be sensibly said. It proposes that many traditional philosophical problems arise from misunderstandings about logic and representation. The opening proposition, "The world is all that is the case", sets the tone: philosophy must begin with what is the case, with facts rather than things, and with how language meaningfully depicts those facts.

Structure and Aim
The book is organized into seven hierarchically numbered propositions. Each main proposition is unfolded through sub-propositions that clarify logical relations, representation, and the boundaries of sense. The project ties together logic, semantics, and metaphysics: by articulating the logical form common to world and language, it explains how statements have meaning and truth, and where meaningful discourse stops.

Picture Theory of Language
Central is the picture theory: a proposition is a logical picture of a possible state of affairs. Just as a spatial model can depict the arrangement of objects, a proposition mirrors the structure of a situation in logical space. Names correspond to simple objects; elementary propositions assert combinations of these objects in states of affairs; complex propositions are truth-functions of elementary ones. Representation requires a shared logical form between language and world. That form cannot be said; it is shown in the possibility of mapping elements of the proposition onto elements of reality.

Facts, Objects, and Logical Space
The world consists of facts, not mere things. Facts are existing states of affairs, combinations of objects that could be otherwise. Objects are simple, indefinable, and provide the substance of the world; they determine the bounds of logical space by fixing what combinations are possible. Sense depends on determinate reference: a proposition has meaning only insofar as its constituents are properly linked to objects, and its logical articulation is clear.

Logic, Tautology, and Necessity
Logical truths are tautologies: they say nothing about the world yet show the scaffolding of logical space. Likewise, contradictions are senseless. Necessity is not a feature discovered in the world but a product of logical form. Logic does not state facts; it provides the rules that enable meaningful statement. The truth-functional account of connectives shows how complex sense arises from the combinatorial possibilities of elementary propositions.

Subject, World, and Solipsism
The metaphysical subject is not a thing within the world but the limit of the world, akin to how the eye is not in the visual field. Solipsism, when properly understood, converges with realism: the limits of my language are the limits of my world, yet the structure of representation is impersonal. What can be said is, in principle, sayable by anyone who shares the logical form.

Philosophy, Ethics, and the Mystical
Philosophy is not a doctrine but an activity: it clarifies propositions, dissolves confusions, and distinguishes sense from nonsense. Ethical, aesthetic, and metaphysical attempts to say what lies beyond the world of facts result in nonsensical sentences, not because the matters are trivial, but because they cannot be put into propositions. Value does not exist among facts; it shows itself. Hence the famous injunction: "Whereof one cannot speak, thereof one must be silent".

Method and Self-Undermining Ladder
The text ends by likening itself to a ladder to be climbed and then thrown away. Its propositions are tools for achieving clarity about language and logic; once the reader sees aright, the propositions can be recognized as nonsensical in the same way they diagnose other philosophical sentences. The legacy is a stringent criterion of sense that shaped analytic philosophy and a haunting sense that what matters most resists propositional expression.