I just ran across the sentence “Unicorns don’t have wings.” It
strikes me as a good example of the sticky problem of truth-
conditions. We say that a statement is well-formed iff it
describes a possible world. It is true iff it describes an
actual situation in that possible world. You can say “Harry
Potter has a scar” and this is true because in the possible
world of Harry Potter (yes, we have a loose definition of
“possible” here) he does have a scar. You can say “Harry Potter
is married to Hermione,” and although well-formed, this
statement is false. The statement to be true need not describe
this world, merely one that is “possible.” In a possible world
with unicorns, the statement “Unicorns don’t have wings” is
true. Similarly, we can say “There is no such things as
unicorns” and this statement is true. But what if you say
*”Unicorns don’t have wings, and there is no such thing as
unicorns.” That doesn’t even seem well-formed; it’s neither true
nor false, but meaningless. And if you reverse it, it’s even m