Logic and Language, Terms, Propositions and Classification of Propositions
This domain examines how language carries logical form: the shift from words to terms, from sentences to propositions, and the classification of propositions by relation, quantity, quality and simplicity. The exam tests precise use of term, proposition, categorical, hypothetical and disjunctive.
Core rules
- A term is a word or phrase functioning as subject or predicate in a proposition. Its connotation is the set of attributes it implies; its denotation is the class of objects it names.
- A proposition is truth-apt; a sentence is a grammatical unit. Different sentences can express the same proposition, and questions, commands and exclamations are not propositions.
- Categorical propositions assert an unconditional relation between subject and predicate. Hypothetical propositions are conditional; disjunctive propositions present alternatives.
- Simple propositions contain one subject-predicate relation; compound propositions contain more than one. Propositions may be universal, particular or singular, and affirmative or negative.
Worked example
Some honest lawyers are not wealthy. The subject term is honest lawyers; the predicate term is wealthy people. The proposition is particular in quantity because some means at least one but not all, and negative in quality because of not. It is a categorical O proposition, not a hypothetical one. Its truth depends on whether at least one member of the subject class lies outside the predicate class.
Traps
Do not confuse a word with a term: a term has a logical role. Do not call every sentence a proposition. Treat only, unless and not all carefully: only citizens can vote means all voters are citizens; not all S are P means some S are not P. Do not mistake inclusive or for exclusive or without context.