As with my previous post, this post is another excerpt that will be included in my final Master’s thesis, but I decided it is interesting enough to post it on its own.
We start with a definition of diagonalization (or quotation), as discussed in The Gödelian Puzzle Book:
Definition 1: For an expression in which a variable
occurs, we say that its diagonalization
is the substitution of the variable
with the quoted expression
.
This definition allows us to represent self-referential expressions.