To every ?-consistent **recursive** class ? of formulae there correspond **recursive** class signs r, such that neither v Gen r nor Neg (v Gen r) belongs to Flg (?) (where v is the free variable of r).

— Proposition VI,

— Informally, recursive systems of axioms cannot be complete.

God wrote in Lisp code When he filled the leaves with green. The fractal flowers and **recursive** roots: The most lovely hack I've seen.

— Bob Kanefsky, "Eternal Flame" [1]

LISP is now the second oldest programming language in present widespread use (after FORTRAN )... Its core occupies some kind of local optimum in the space of programming languages given that static friction discourages purely notational changes. **recursive** use of conditional expressions, representation of symbolic information externally by lists and internally by list structure, and representation of program in the same way will probably have a very long life.

— John McCarthy (1974) "History of Lisp," as quoted in: Avron Barr, Edward Feigenbaum.