Actually, we're engaged "in theory."
Oh, that's great, congratulations. I'd explain it to Collette if I spoke French, and understood what you were talking about.
Why is everyone having such a tough time with this? It's very simple - an engagement is a promise to be married. and I am promising to be engaged, which in theory is a promise to be married, hence we are engaged in theory.
Good luck finding a card for that.