You know him to be a quack and a rogue, and he knows you know it.

But he wriggles on his way, and leaves a track of slimy flattery after him wherever he goes.

Who can penetrate that man's mystery?
What earthly good can he get from you or me?
You don't know what is working under that leering tranquil mask.

You have only the dim instinctive repulsion that warns you, you are in the presence of a knave--beyond which fact all Fawney's soul is a secret to you.
I think I like to speculate on the young men best.

Their play is opener.
You know the cards in their hand, as it were.