Definition
Reference is the relation that links a name or descriptive expression to the particular thing it stands for. The name "Socrates" refers to a specific philosopher; the phrase "the capital of France" refers to Paris. Reference is how language reaches out and latches onto the world.
In logic, reference matters because the truth of many statements depends on what their terms refer to. An argument's validity can hinge on whether two names pick out the same object, or on whether a name picks out anything at all.
Why it matters
How it works
A name that successfully refers contributes its object to the statement, and the statement is then true or false depending on how that object behaves. Trouble arises with non-referring terms: "the present King of France" picks out nobody, so it is unclear whether "the present King of France is bald" is true, false, or neither.
Priest also flags a subtler puzzle. Reference seems to support free substitution — swapping one name of an object for another should not change truth value — yet inside contexts like "Lois Lane believes that..." it can. These phenomena show that reference, far from being a trivial pointing relation, raises some of the deepest questions in the philosophy of logic and language.