Rudolf Carnap

Rudolf Carnap is the cleanest mind of the formalist century, and his thought is indispensable for the age of artificial intelligence not because he was right but because he was wrong in the most instructive places. The first half-century of AI—the expert systems, the knowledge representation schemes, the logical inference engines—was an attempt to build, in silicon, the program he drew in his 1928 masterwork Der logische Aufbau der Welt: a complete reconstruction of all knowledge from explicit primitives and logical rules. His criterion of meaning argued that a sentence has content only if some possible observation could confirm or refute it—and that criterion ate itself, failing to survive contact with universal scientific laws, let alone the judgments that govern a human life. His sharp line between truths of language and truths of fact, the analytic-synthetic distinction, was demolished by his own friend Quine in a paper every philosophy student still reads. And his program left out, by design, the entire