||It seems that it's possible for Mary to utter the sentence ‘Whales are fish’ and thereby say that whales are fish. John might believe what Mary said, or not. If John and Mary both believe it then there is something that they both believe. That thing is false, however. That Mary can use that sentence to say that might be partly explained by the fact that ‘Whales are fish’ means that whales are fish. (The fact that Mary can use that sentence to convey that John doesn’t know much about Whales by adopting a certain tone of voice might also be partly explained by that meaning fact.) The preceding claims are not self-evident, but they are attractive. Taken at face value they suggest that there is a class of objects which can be believed, said, take truth values and serve as meanings. The standard name for such things is ‘propositions’. There are several debates at the intersection of philosophy of language, philosophy of mind, and metaphysics about the nature of these entities and the roles they should play in our philosophical theories.