but consider: if a sufficiently magical technology could make an atom-for-atom copy of the mona lisa, we would still feel that there was some quality that disti

but consider: if a sufficiently magical technology could make an atom-for-atom copy of the mona lisa, we would still feel that there was some quality that distinguished the original. the most satisfying solution I've seen is to consider an "object" as a four dimensional world line, elevating "position x at time t" to an intrinsic property. that keeps the two spheres distinct even if they swap positions, since they would never swap world lines.