Imagine: you are window-shopping on a quiet street, perhaps in London or Paris or New York. Something remarkable catches your eye: an ancient coin, a gold chain, a tiny figurine. Impulsively, you enter the shop, where the owner explains to you that the sculpture comes originally from Mesopotamia, that the necklace is Byzantine. It isn’t inexpensive, but the shopkeeper has guaranteed its provenance and the price seems fair; and besides, you quite love it. You say yes, and leave the shop with your new treasure tucked safely in a bag.
You may have just handed your money over to the Islamic State.