I have had the pleasure of your acquaintance long enough to know that you find great enjoyment in occasionally professing opinions which in fact are not your own.
– Jane Austen
Pride and Prejudice, Chapter 31. When Darcy says this to the headstrong Elizabeth, he is suggesting that in some of her sparring with him she is putting on an act and not being entirely herself. He feels that to prove her point she is saying things that she doesn’t fully believe.