 Propositions, taken as the contents or meanings of sentences, have often been interpreted starting from Wittgenstein’s insight that understanding a sentence is knowing what is the case if it is true (Wittgenstein 1921: 4.024). Truth conditions have been given via sets of possible worlds in the SPWS approaches of Montague (1970), Stalnaker (1976) and many others: the proposition expressed by “St Andrews is rainy” is the set of worlds where St Andrews is rainy.