 One worry about the left-to-right direction of  Duplication  is based on the fact that, under plausible assumptions, it entails that duplicate objects must always have exactly the same perfectly natural  properties.[18]  This is in tension with certain unorthodox views about perfect naturalness, e.g. that specific location properties (e.g. being here) or vector properties (e.g. moving in this direction) are perfectly  natural.[19]  Proponents of such views might consider modifying  Duplication  to allow certain nontrivial permutations of perfectly natural properties.