 action-based theories of perception |  Cohen, Hermann |  color |  Duhem, Pierre |  geometry: in the 19th century |  Herbart, Johann Friedrich |  Lange, Friedrich Albert |  Lotze, Hermann |  measurement: in science |  Molyneux’s problem |  neo-Kantianism |  physics: experiment in |  quantum theory: philosophical issues in |  Schlick, Moritz |  Stumpf, Carl |  Wundt, Wilhelm Maximilian 