Richard Zach

The model and proof theory of classical first-order logic are a staple of introductory logic courses: we have nice proof systems, well-understood notions of models, validity, and consequence, and a proof of completeness. The story of how these were developed in the 1920s, 30s, and even 40s usually consists in simply a list of results and who obtained them when. What happened behind the scenes is much less well known. The talk will fill in some of that back story and show how philosophical, methodological, and practical considerations shaped the development of the conceptual framework and the direction of research in these formative decades. Specifically, I’ll discuss how the work of Hilbert and his students (Behmann, Schönfinkel, Bernays, and Ackermann) on the decision problem in the 1920s led from an almost entirely syntactic approach to logic to the development of first-order semantics that made the completeness theorem possible.

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