Carnap, Logicism, and Ontological Commitment

In a number of works, Rudolf Carnap provided ingenious and systematic approaches to the understanding of scientific knowledge (see, for instance, Carnap 1928, 1934, 1947, 1950a, b). As is well known, his proposals faced three important changes: (i) the early phenomenalism of the Logische Aufbau der Welt (Carnap 1928) was replaced by the physicalism of Logische Syntax der Sprache (Carnap 1934); (ii) the primarily syntactic account of Logische Syntax was then replaced by the semantic and modal views of Meaning and Necessity (Carnap 1947); and (iii) the deductivism that characterized Carnap’s early work was eventually replaced by the probabilism of Logical Foundations of Probability (Carnap 1950a). These shifts in philosophical perspective occurred against the background of the explicit use of mathematical and logical techniques, and they were articulated to preserve an essentially empiricist attitude towards science. The commitment to empiricism remained unchanged throughout Carnap’s career.