A theory: The English sentence “Today is a Thursday” has the same meaning on all days when it is spoken, but its truth-value varies depending on when it is spoken. (The sentence always corresponds to the same proposition, but that proposition has variable truth value).
B theory: The English sentence “Today is a Thursday” means something different when it is spoken on different occasions. Each specific utterance has a truth value which never changes. (Again, each utterance corresponds to a different proposition, but any one such proposition always has the same truth value.)
If you can live with propositions whose truth value changes with time, then you’re probably an A-theorist. If something smells fishy about that, and you think that in any given possible world, a proposition is either true or false and never changes its truth value, you’re probably a B-theorist.
Here’s maybe another way of thinking about it …
A theory: The English sentence “Today is a Thursday” has the same meaning on all days when it is spoken, but its truth-value varies depending on when it is spoken. (The sentence always corresponds to the same proposition, but that proposition has variable truth value).
B theory: The English sentence “Today is a Thursday” means something different when it is spoken on different occasions. Each specific utterance has a truth value which never changes. (Again, each utterance corresponds to a different proposition, but any one such proposition always has the same truth value.)
If you can live with propositions whose truth value changes with time, then you’re probably an A-theorist. If something smells fishy about that, and you think that in any given possible world, a proposition is either true or false and never changes its truth value, you’re probably a B-theorist.