Lecture 29: Equality

We start a new topic by introducing equality into the logic. We recapitulate the major steps taken in the development of the other logical connectives: natural deduction, normal derivations, proof terms, and sequent calculus. We also consider cut elimination which appears to require a restricted form of derivation where equality inferences appear above all other inferences.

Reading

• Pages 107-111 of Handout 16 on Equality (also availabe in PDF format).

Key Concepts

• Reflexivity
• Substitution rule
• Regular derivations

Links

• Previous lecture: Discrimination Trees
• Next lecture: Cut Elimination with Equality