The question of basic and incorrigible sentences has appeared in connection with certain recent attempts to refine and re-define the meaning of Empiricism. More directly still, the question appears in connection with the problem of verification. It is noteworthy that the question of protocols, more than any other issue, has served to draw out the philosophical differences between the original Wiener Kreis and the Cambridge Analysts. Yet despite their differences both schools are agreed that basic sentences in some sense of the word, are epistemologically necessary.

But if one takes the view, say of the Instrumentalists, that all perceptual knowledge is interpretation based upon accepted theories, and corrected in the light of such theories then basic sentences are quite unnecessary. But among those who employ the term “basic” there is little agreement as to its meaning. The common use of the term has not resulted in a common understanding. And instead of drawing Empiricists together it has succeeded only in driving them apart.