@misc{Lexicon of Arguments, title = {Quotation from: Lexicon of Arguments – Concepts - Ed. Martin Schulz, 28 Mar 2024}, author = {Stechow,Arnim von}, subject = {Extensionality}, note = {61 Extensional propositional logic/Stechow: cannot describe the meaning of "Modals". >Modality, >Modal Logic, >Meaning, >Extension, >Extensionality. E.g. the meaning of "must" is "follows from my knowledge". [[must f]] says in epistemic meaning that [[f]] is a superset of my knowledge. The meaning function [[must]] is a relation between two sets of situations. >Functions, >Situations. Such meanings (sets of possible worlds) we do not have when sentences (extensionally) designate truth values. >Truth values, >Possible worlds, >Intensions.},