Type theory

Internalizing judgemental structure

A well-justified connective (i.e. way of introducing types and their terms) abides the following:

Slogan 2.5.4

A connective in type theory is given by (1) a natural type-forming operation Υ and (2) one of the following:

  1. a natural isomorphism relating Tm(Γ,Υ) to judgementally-determined structure, or
  2. a collection of natural term constructors for Υ which, for all dependent types Γ.Υ 𝐴, determine a natural isomorphism relating Tm(Γ.Υ,𝐴) to judgementally-determined structure.1

The first camp accounts for the most well-behaved connectives, the latter for inductive types.

See also


#state/develop | #lang/en | #SemBr

Footnotes

  1. 2026. Principles of dependent type theory, p. 52. Terminology and notation adapted to that used in these notes.