As the types of objects accepted proliferate, so do the possible tokens that a given collection of matter can be said to instantiate.
For example, any ontology that affirms the existence of tables, rabbits, or rocks necessarily commits to the inclusion of some compositional objects.
Clarification demands that these theories provide a means to account for which compositional objects are included and which are excluded.
Noting the appeal of accepting that things do exist, one must reject mereological nihilism in order to maintain a gunky ontology.
These theories all attempt to specify characteristics that a collection of objects must possess in order to compose a whole.
Many of these accounts appeal to characteristics derived from intuitive notions about what does or does not allow objects to function as parts in a whole.
First, connection is the stipulation that objects must be spatially continuous to some degree in order to be considered parts composing a whole.
In order to maintain the standard of absolute contiguity one would have to recruit the air molecules bridging span between the table and chairs.
This is unsatisfactory though because it fails to exclude extraordinary objects such as the table, the air molecules, and the dog's nose as he begs for food.
By abandoning the extreme of direct contact, any account of connection acquires the burden of defining what degree of proximity instantiates composition.
It will not do to leave specification of degree for future theorists if one cannot even show it is possible to provide such a determination in a principled manner.
According to a moderate formulation of connection, composition is instantiated by two objects separated by a countable number of discrete points (x), where (x) need not be one, but cannot be unbounded.
This approach guarantees the existence of you and me, while ruling out extraordinary objects consistent with other conservative theories.
It is not clear if a virion, a virus particle composed of nucleic acid and surrounding capsid, is a compositional object or not.
Varzi, Achille, "Mereology", The Stanford Encyclopedia of Philosophy (Winter 2016 Edition), Edward N. Zalta (ed.