- All Men are Mortal.
- Socrates is a Man.
- .:. Socrates is Mortal.
A proposition is a declarative sentence in which the predicate is affirmed or denied of the subject. A proposition is the meaning of a declarative sentence. Propositions are either true or false. We indicated above that propositions (and only propositions) are the elements (premises and conclusions) of an argument. Sentences that express commands, pose questions, or convey exhortations are neither true nor false, and therefore are never elements of an argument. Gordon Clark puts it this way:
Of course in English Rhetoric there are questions that are intended as propositions. They are called rhetorical questions. But logically they are propositions. A question that is intended as a question is neither true nor false. It can play no part in an argument.,(Logic, p. 30 PB)