Two-Component Semantics

When do two sentences say the same thing, that is, express the same propositional content? This chapter defends two-component (2C) semantics, the view that propositional contents comprise pairs of irreducibly distinct components: (1) truth conditions, and (2) topic or subject matter. It presents an abstract 2C formal semantics, which gives synonymy conditions while being neutral on the exact nature of subject matter. The chapter compares 2C with 1C semantics, the view that either truth conditions are reducible to subject matter or vice versa, and argues for the superiority of 2C. In order to do so, it develops a ‘topicology’, laying out a series of constraints any good theory of topic or subject matter should obey. In particular, the truth-functional propositional connectives of negation, conjunction, disjunction should be topic-transparent: they should add no topic of their own; and there should be necessary or co-necessary (intensionally equivalent) sentences which express different contents due to differences in topic or subject matter, i.e in what they are about. Finally, the chapter explores some difficulties for the idea that coincidence in truth conditions and topic is both necessary and sufficient for content identity.