Tractatus Logico-Philosophicus · Chapter
6.1201 explained
Wittgenstein illustrates how tautologies reveal logical relations between propositions, such as contradiction, consequence, and instantiation, by examining specific logical forms.
What happens
Wittgenstein illustrates how tautologies reveal logical relations between propositions, such as contradiction, consequence, and instantiation, by examining specific logical forms.
Themes in this chapter
Logic and Tautology
The chapter uses tautologies to exhibit logical relations like contradiction and consequence between propositions.
Characters to notice
- Mr. Wittgenstein
Author of the Tractatus, presenting examples of tautologies to demonstrate logical relations.
Key passages
“That e.g. the propositions “ p ” and “ ~ p ” in the connection “ ~ ( p . ~ p ) ” give a tautology shows that they contradict one another.”
The fact that 'not (p and not p)' is a tautology demonstrates that p and not p are contradictory.
Illustrates contradiction via tautology.
“That the propositions “ p ⊃ q ”, “ p ” and “ q ” connected together in the form “ ( p ⊃ q ) . ( p ) : ⊃ : ( q ) ” give a tautology shows that q follows from p and p ⊃ q .”
The tautology of the conditional form shows that q is a logical consequence of p and 'if p then q'.
Demonstrates logical consequence through tautology.
“That “ ( x ) . f x : ⊃ : f a ” is a tautology shows that f a follows from ( x ) . f x , etc. etc.”
The tautology 'if everything is f, then a is f' shows that the particular instance follows from the universal statement.
Shows instantiation as a logical relation via tautology.