# 3.311 explained — Tractatus Logico-Philosophicus

> Chapter companion for Tractatus Logico-Philosophicus by Ludwig Wittgenstein.

## What happens

Wittgenstein defines an expression as that which presupposes the forms of all propositions in which it can occur, serving as the common characteristic mark of a class of propositions.

## Themes in this chapter

### Logical Atomism

The notion of expressions as presupposing forms aligns with the logical atomist view of propositions as composed of simple elements.

## Character check-ins

### Mr. Wittgenstein

Author of the proposition, defining the nature of expressions in logical syntax.

## Key lines

> An expression presupposes the forms of all propositions in which it can occur.

An expression inherently requires the logical forms of every proposition that can contain it.

_Clarifies the dependency of expressions on propositional forms._

> It is the common characteristic mark of a class of propositions.

An expression serves as the shared feature that defines a set of propositions.

_Defines expressions as classifiers of proposition types._

## Links

- HTML: https://www.betterreads.online/discover/tractatus_logico_philosophicus_se/chapters/3-311
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- All chapters: https://www.betterreads.online/discover/tractatus_logico_philosophicus_se/chapters