5.143 Contradiction is the common property of propositions, what no proposition has in common with another. Tautology is the common property of all propositions that have nothing in common with one another.

Contradiction vanishes, so to speak, outside, tautology inside, all propositions.

Contradiction is the outer limit of propositions, tautology their substanceless center.

Very strange. It is common to all propositions that none of them have contradictions in common, and that is what contradiction is. Tautologies are equally strangely ‘defined’ here. Both vanish (verschwinden: vanish, disappear, be lost, pass away), so to speak. One is outside all propositions, the other without substance. How close we are to saying that the notions are quite without meaning. I suppose you could tag the denial of a contradiction onto any proposition, or the affirmation of a tautology.