A proposition is the expression of agreement and disagreement with the truth-possibilities of the elementary propositions.
4.41 (1) The truth-possibilities of the elementary propositions are the conditions of the truth and falsehood of the propositions.
4.42 With regard to the agreement and disagreement of a proposition with the truth-possibilities of n elementary propositions there are possibilities.
4.43 (1) Agreement with the truth-possibilities can be expressed by co-ordinating with them in the scheme the mark "T" (true).
Absence of this mark means disagreement.
4.44 (2) The sign which arises from the co-ordination of that mark "T" with the truth-possibilities is a propositional sign.
4.45 For n elementary propositions there are Ln possible groups of truth-conditions.
The groups of truth-conditions which belong to the truth-possibilities of a number of elementary propositions can be ordered in a series.
4.46 (6) Among the possible groups of truth-conditions there are two extreme cases.
In the one case the proposition is true for all the truth-possibilities of the elementary propositions. We say that the truth-conditions are tautological.
In the second case the proposition is false for all the truth-possibilities. The truth-conditions are self-contradictory.
In the first case we call the proposition a tautology, in the second case a contradiction.