In like manner, bundle theory has been charged with ruling out the possibility of change in objects. The same bundle complex cannot be composed of one set of property at one time, but a different set at a different time. Concrete objects, on the other hand, can and do change. In response, it has been suggested that this objection loses its force if bundle theory is combined with a four-dimensionalist account of object persistence (Casullo 1988; see also Ehring 2011). For example, if ordinary objects are spacetime worms made up of appropriately related instantaneous temporal parts that are themselves complete bundles of compresent tropes, then change can be read as a matter of having different temporal parts that differ in their constitutive properties. Another response to the change-is-impossible objection is to adopt Simons’ “nucleus theory” in place of traditional bundle theory. Nucleus theory seems to allow for change in the outer band of accidental properties (Simons 1994).