 The properties that the forgery is guaranteed to share with the original are those that supervene upon its microphysical properties. Two paintings that are microphysically just alike are guaranteed to be just alike in the arrangement of colors and shapes on their canvases. That is, you cannot change the arrangement of colors and shapes on a painting’s canvas without changing its microphysical properties. This is just to say that the arrangement of colors and shapes supervenes on its microphysical properties.