The modal interpretation of algebraic quantum field theory

Abstract We show that Dieks' recent proposal for extending the modal interpretation to algebraic quantum field theory fails to yield a well-defined prescription for which observables in a local spacetime region possess definite values. On the other hand, we demonstrate that there is a well-defined and unique extension of the modal interpretation to the local algebras of quantum field theory (which may, however, face a serious difficulty in connection with ergodic field states).