Chisholm concludes this discussion by saying that “these reflections, on the consequences of extreme mereological inessentialism, may suggest to us that some version of mereological essentialism must be true…” (586). In the remaining pages of the paper Chisholm presents a view according to which extreme mereological essentialism is true — but only for what he calls “primary objects”. Ordinary or “vulgar” objects such as tables and ships are not primary objects. Each such vulgar object may be understood to be a gradually evolving sequence of primary objects. The vulgar object is constituted by different primary objects at different times. Vulgar objects can gain and lose parts across times and possible worlds. Mereological essentialism is not true for them.