Abstract
Semirealism divides the properties of unobservables into two types: detection properties and auxiliary properties. Detection properties represent the causal properties of an unobservable entities by which its existence can be detected. On the other hand, auxiliary properties are not involved in detection. Semirealism holds that science gives us knowledge of detection properties but not auxiliary properties. In the present paper, I interpret algebraic quantum field theory from a semirealistic point of view. Especially I investigate localized states, which was introduced by Knight (1961) and Licht (1963). Roughly speaking, a localized state represents a localized excitation of the vacuum. I formulate a detection of a localized excitation, and show that this detection does not exist in algebraic quantum field theory.
