 Perhaps the set theorist can instead maintain that masses are sets, but deny that sets (or at least sets of bits of matter) are abstract. A set theorist might maintain that sets of physical objects (such as gold atoms) can be said to be in space in virtue of their members being in space. The gold, construed as a set of gold atoms, can be said to weigh ten ounces in virtue of its members collectively weighing ten ounces. On this kind of view, massy sets have their physical properties ‘by proxy’ (Zimmerman 1995, sections 3 and 9).