In 1934 Charles W. Morris, then a young philosopher at the University of Chicago, visited Rudolf Carnap in Prague, where the latter was teaching on the science faculty of Charles University. Morris, a philosopher familiar with Peirce's work and himself following the traditions of pragmatism, was impressed with the positivist program. Two years later he played an impor tant role in Carnap's move to a professorship at the University of Chicago.1 In the following year, 1937, Hermann in Paris published a slim but eloquent book by Morris, Pragmatism, Logical Positivism, and Scientific Empiricism. Its thesis was that American pragmatism and European positivism were en tirely complementary philosophical movements, and that the collaboration of the adherents of the two could lead to a new form of scientific empiricism more fruitful than either. Carnap did give this suggestion of Morris cautious lip service in Testability and Meaning,2 his first important paper in the United States. But active intellectual collaboration between members of these two philosophical movements did not, in fact, occur. Indeed, as philosophy developed after the disruptions of World War II, relationships between members of the two groups might best be characterized as marked by mutual misunderstandings and distaste. Morris abandoned his hopes for their fusion and turned his attention to other matters, Carnap continued to develop his own views, and only the International Encyclopedia of the Unified Sciences, which they founded together, remains to testify to such a vision. Without commenting further on what might have been, and the social and political reasons why it may have failed to come about, let us look at those aspects of theory and outlook shared by the two movements, as well as those on which they differed, and see what the substantive problems were. For reasons of simplicity and breadth of scope, attention will be focused on the theories of Peirce and Carnap, with special attention to the details of Peirce's views where these are not as widely known. It is hard to look at the work of Peirce (1839-1914) and Carnap (1891? 1970) without being impressed, as Morris was, by the similarity of spirit they seemed to share?in spite of the fifty years that separated their lives.