How does Tom know the man he meets in the forest is the devil?

The man he meets in the forest tells him that this land belonged to him long before any of Tom's people claimed it. Tom asks who he is, and he says he goes by various names; he is the wild huntsman in some countries, the black miner in others, but here he is known as the black woodsman. He says that Indians consecrated this land in his name, and since "white savages" exterminated the Indians, he is their great patron. He also says he presides at the persecutions of Quakers and Anabaptists. Tom realizes that this is the man commonly called "Old Scratch."