Can a sum change its parts?
D. H. Sanford · Analysis · 2011
There are sums of many kinds. All the sums in this article are mereological sums, so I will usually omit the adjective ‘mereological’. Here is a definition of ‘x is a sum of the ys’: DEF: The ys are all parts of x, and every part of x has a part in common with at least one of the ys. The ys are all parts of x, and every part of x overlaps at least one of the ys (van Inwagen 2003: 618). Everything that overlaps x overlaps y.