The debate between 3- and 4-dimensionalists is one of the most lively and pervasive in current metaphysics. At stake is a glittering prize: the correct metaphysical analysis of material things and other objects commonly thought to persist in time by enduring. Since we count ourselves among such objects the outcome of the debate is of more than merely academic interest to us. Obviously the ramifications of the debate, even of the points raised by Kit Fine, go far beyond what I can discuss here, so I shall simply select some salient issues and comment on them from my own somewhat heterodox point of view.

In ‘Two Notions of Being: Entity and Essence’ E. J. Lowe defends “serious essentialism”. Serious essentialism is the position that (a) everything has an essence, (b) essences are not themselves things, and (c) essences are the ground for metaphysical necessity and possibility. Lowe's defence of serious essentialism is both metaphysical and epistemological. In what follows I use Lowe's discussion as a point of departure for, first, adding some considerations for the plausibility of essentialism and, second, some work on modal epistemology.

Entities of many kinds, not just material things, have been credited with parts. Armstrong (1978: 36), for example, has taken propositions and properties to be parts of their conjunctions, sets to be parts of sets that include them, and geographical regions and events to be parts of regions and events that contain them. The justification for bringing all these diverse relations under a single ‘part–whole’ concept is that they share all or most of the formal features articulated in mereology (Simons 1987). But the concept has also prompted an ontological thesis that has been expressed in various ways: that wholes are ‘no ontological addition’ to their parts (meaning their proper parts, i.e. not counting a whole as a part of itself); that to list both a whole and its parts is ‘double counting’; and that there is ‘no more’ to a whole than its parts: for example, that there is no more to a conjunction (i.e. to its truth conditions) than the conjuncts that are its parts, and whose truth or falsity determines whether it is true or false. For brevity, I shall express the thesis in the last of these ways, as the claim that entities with parts are ‘nothing but’ those parts.

Whenever a material thing has parts, those parts are located where that thing is. This is a necessary truth, and needs explaining.

Together, these entail that for every true proposition p, there exists some thing which could not exist and p be false.

Exotic ontologies are all the rage. Distant from common sense and often science as well, views like mereological essentialism, nihilism, and four-dimensionalism appeal to our desire to avoid arbitrariness, anthropocentrism, and metaphysical conundrums.

This paper is about a puzzle concerning the metaphysics of material objects: a puzzle generated by cases where material objects appear to coincide, sharing all their matter. As is well known, it can be illustrated by the example of a statue. In front of me now, sitting on my desk, is a (small) statue – a statue of a lion. The statue is made of clay. So in front of me now is a piece of clay. But what is the relation between the statue and the piece of clay? Are they identical, or are they distinct?

Last weekend, I made a bookcase. To begin with, I went and bought various pieces of wood and several screws. Then I screwed the pieces of wood together. In doing so, I created something new: my bookcase. And this bookcase is made up of the pieces of wood and the screws. In other words, they're parts of it.

Roughly speaking, perdurantism is the view that ordinary objects persist through time by having temporal parts, whilst endurantism is the view that they persist by being wholly present at different times. (Speaking less roughly will be important later.) It is often thought that perdurantists have an advantage over endurantists when dealing with objects which appear to coincide temporarily: lumps, statues, cats, tail-complements, bisected brains, repaired ships, and the like. Some cases – personal fission, for example – seem to involve temporary coincidence between objects of the same kind. Other cases – a cat and its flesh, a statue and its lump – seem to involve objects of different kinds.