On protocol sentences

In the preceding article of the same title, Otto Neurath has again raised the question of protocol sentences. This question constitutes the core problem of the logic of science, that is of the theory of knowledge, for it comprises the questions dealt with under the terms "empirical foundation", "testing" and "verification". For physicalism it is especially urgent to justify protocol sentences and thereby the experiential foundation of science. This is where most doubt about physicialism begins, and indeed it is the really critical point for this view. Neurath opposes certain features of the view about protocol sentences I advocated in my article on the physicalistic language (Erkenntnis, vol. II, p. 432). He wants to contrast it with another view according to which protocol sentences are in a different form and are manipulated according to other procedures. My opinion here is that this is a question, not of two mutually inconsistent views, but rather of two different methods for structuring the language of science both of which are possible and legitimate. In what follows both procedures will be described more precisely, and this will show that each of them has certain advantages. The first language form affords greater