15-317 Constructive Logic
Lecture 18: Cut Elimination

In this lecture we discuss the central properties of the sequent calculus, namely cut and identity. These correspond to global version of the local soundness and completeness properties, respectively. We also sketch the essential ideas in the proof of the admissibility of cut and give some important applications for this theorem.

• Reading: atp:ch3-seqcalc.pdf, Sec 3.4-3.5
• Previous lecture: Sequent Calculus
• Next lecture: Metainterpreters
• Key concepts:
  • Identity
  • Cut
  • Invertibility
  • Consistency
  • Disjunction property
  • Existential property

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Frank Pfenning