This SEP article on mereology is instructive relative to OOO's strange version. (Warning: math involved.) For example:
"Mereologically, an atom (or 'simple') is an entity with no proper parts, regardless of whether it is point-like or has spatial (and/or temporal) extension.... Are there any such entities? And if there are, is everything entirely made up of atoms? Does everything comprise at least some atoms? Or is everything made up of atomless 'gunk' (in the terminology of Lewis 1970)? These are deep and difficult questions, which have been the focus of philosophical investigation since the early days of philosophy."
Also of import is that a main premise of most mereology is the principle of identity, which premise is under question in OOO. "All the theories examined above...appear to assume that parthood is a perfectly determinate relation." Note the presuppositions of mereology in this statement: "These worries are of no little import, and it might be thought that some of the principles discussed above would have to be revisited accordingly...because of their classical, bivalent presuppositions."
This has to do with precise boundaries and the article explores how these can be fuzzy and indeterminate. Hence phrases like "unbounded wholeness" are contradictory (or complimentary, if you prefer) since it is a whole without a defining boundary and hence itself is not a "part" of anything. Unless of course each part of "it" retains this characteristic indeterminate openness (withdrawal), in which case things (processes, suobjects) aren't as tidy as we might suppose.
What "level" recognizes this? I agree somewhat with Tom in that the notion of levels itself comes under question at this point since it too is part and parcel (pun intended) of tidy boundaries.
Quick comment on the Bortoft quotes (see thread). He recognizes that we cannot know the whole in the same way that we know the parts, for it is indeterminate. And that the whole can only be known through the parts. However he doesn't seem to acknowledge that this same indeterminacy of the whole is also in the parts in that we cannot know them fully either via identity, as they too are withdrawn from themselves.
From Mind and Nature, being discussed in this thread:
“Categories are wholes to their members, which become wholes to subsidiary members, and so on, in a progression that is bottomless....the continuum is a transition from a category (whole) to an instance (part) where the latter is the basis of another transition. The transition has the character of an emergence of whole-like parts from part-like wholes, where the wholes are not mere collections, and the parts are not definite elements but the potential to form subsequent wholes. The whole-part relation is a successive nesting that finally terminates in a concrete part, an actuality, that does not serve as a whole for a further transformation.... The relation of whole to part is that of a recursive embedding of potentialities” (7)
For Brown the Core is unbounded wholeness in potentia, which then informs the particular. Then lesser and greater (relative) wholes take shape, but all arising from the absolute assholon. I'm yet again reminded of the difference in “what 'is' the differance?”, which highlights another Yogacara doctrine.
Although it seems strange that particular instances are “the basis of another transition,” with transition being defined as a whole-to-part process. And yet when a part becomes a “concrete actuality” it no longer serves “as a whole for further transformation”? Have we arrived at the “atom” (object) with no further parts?