2.8 Tutorial: Identifying Necessary and Contingent Statements

Recall from the text that some statements are true solely by definition of the terms in them (‘necessary true’ or ‘tautology’), and some are false by definition of the terms in them (‘necessarily false’ or ‘self-contradictory’). Necessary statements (i.e., tautologies and self-contradictions) are uninformative about the world since they don’t depend on the way the world is. In contrast, a statement can be true not necessarily but because of the way the world is (‘contingently true’) or false because of the way is (‘contingently false’). Because their truth depends upon the way the world is and not merely upon the meanings of the words involved, contingent statements are informative.

For each of the following sentences, assume that any terms used in it are consistently defined or interpreted. (For example, by “Maria is Maria” we mean the same person for both uses of the word ‘Maria’). Determine whether the statement is a tautology, self-contradiction, contingent truth, or contingent falsehood.