Incorporating Quotation and Evaluation into Church's Type Theory: Syntax and Semantics

${\rm \small CTT}_{\rm qe}$ is a version of Church's type theory that includes quotation and evaluation operators that are similar to quote and eval in the Lisp programming language. With quotation and evaluation it is possible to reason in ${\rm \small CTT}_{\rm qe}$ about the interplay of the syntax and semantics of expressions and, as a result, to formalize syntax-based mathematical algorithms. We present the syntax and semantics of ${\rm \small CTT}_{\rm qe}$ and give several examples that illustrate the usefulness of having quotation and evaluation in ${\rm \small CTT}_{\rm qe}$. We do not give a proof system for ${\rm \small CTT}_{\rm qe}$, but we do sketch what a proof system could look like.