 By 1934, the year of the completion of his Logic of Scientific Discovery (Logik der Forschung), Popper had adopted an approach to scientific knowledge based on the logic of method, not on meaning, so that any talk of individual experience would have no linguistic expression (Popper 1935/1951). He unfairly criticized Neurath and also Carnap for allowing with such expressions the introduction of psychologism in a theory of knowledge. For Popper a theory of scientific knowledge was to be not a subjective or descriptive account, but a normative logic of justification and demarcation. He also criticized Neurath’s antifoundationalism about protocols as a form of anti-empiricism that merely opened the door to dogmatism or arbitrariness.