A Contrarian I Once Knew

I once knew a highly contrary fellow. But he was intelligent and interesting and I enjoyed talking with him on occasion. If I asserted proposition p, he would more likely than not assert not-p. If I asserted not-p, then I could expect to hear the assertion of p.

One day I said, "You know, John, you are a really contrary fellow!"

He shot back, "No I’m not!"