The Pessimistic Induction (PI) states: most past scientific theories were radically mistaken; therefore, current theories are probably similarly mistaken. But mistaken in what way? On the usual understanding, such past theories are false. However, on widely held views about reference and presupposition, many theoretical claims of previous scientific theories are neither true nor false. And if substantial portions of past theories are truth-valueless, then the PI leads to semantic antirealism. But most current philosophers of science reject semantic antirealism. So PI proponents face a difficult choice: accept either semantic antirealism or an unorthodox position on reference and presupposition.