Gabbay–Pitts NEW quantifier (fresh-ness)

If you type this into LaTeX...

\usepackage{graphics} %needed for the NEW quantifier \newcommand\new[0]{\reflectbox{\ensuremath{\mathsf{N}}}} %The quantifier itself, a reversed sans-serif N %(by analogy with the reversed E of `exists' %and the reversed A of `forall') \newcommand\New[1]{\new #1.} %A macro, as in \New{a}\phi The $\new$ quantifier

... you get this:
This is not a russian letter! It is a reflected sans-serif roman letter, by analogy with ∀ the reflected A of ‘for all’ and ∃ the reflected E of ‘exists’.

I wish I'd thought of this pun but it's one of Andrew Pitts's ideas. When we discovered (invented?) the NEW quantifier, he suggested a backwards N notation, and this impressed me very deeply. Simple and commonsense can also be brilliant — even in computer science. I made a mental note.