Van Inwagen's *Material Beings* (1990) defends the most precisely formulated version of mereological nihilism the analytic tradition has produced. There are no chairs, no tables, no planets, no stones: only simples arranged chair-wise, table-wise, planet-wise, stone-wise. The single exception is living organisms, whose self-maintaining causal activity Van Inwagen takes to ground a unity mere arrangements lack. The position shrinks the ontology where Lewis's plurality ([§4.4.1](<4.4.1 Modal Realism.md>)) multiplies it, and it does so with the same systematic care. Sider's "Against Parthood" (2013) presses one step further: even the organism exception is rejected, and what remains is only simples in arrangements.

Mereological nihilism (also called compositional nihilism or compositional eliminativism) has a precise lineage. Classical mereology (Leśniewski 1916; Tarski 1929) supplies the formal vocabulary of parthood, and Lewis's *Parts of Classes* (1991) systematizes the contemporary defense of unrestricted composition the nihilist most directly opposes. Van Inwagen (*Material Beings*, 1990) develops the organism-exception version with the most systematic care. Merricks's *Objects and Persons* (2001) extends Van Inwagen's exception to persons and presses the overdetermination argument against composite objects more broadly. Sider's "Against Parthood" (2013, *Oxford Studies in Metaphysics* vol. 8) develops the strictest nihilist version: no composites at any level, organisms included. Dorr's "What We Disagree About When We Disagree About Ontology" (2005) defends compositional nihilism through paraphrase: nihilist and non-nihilist sentences can be made truth-conditionally equivalent. Cameron's "Truthmakers and Ontological Commitment" (2008) develops a kindred deflationary line. Against the nihilists: Markosian's "Brutal Composition" (1998) treats composition as a brute fact admitting no further criterion; Schaffer's "On What Grounds What" (2009) and the monist literature (Schaffer 2010) defend the cosmos as the fundamental composite from which parts derive; classical mereology (Goodman 1951; Simons's *Parts*, 1987) defends unrestricted composition. The structural account sits closest to the moderate-OSR line of [§4.3.9](<4.3.9 Structural Realism.md>) in being neutral on composition while specific about what any arrangement must instantiate.

The nihilist pressure bears on Φ specifically and on the [§2.7](<2.7 Nothing to Consider.md>) architecture more generally. If composite objects do not exist, then the persistent configurations the argument has been describing (patterns of features held together as one substantial bearer across temporal succession) have no bearer to inhere in. T and S might survive as relational facts among simples, but Φ, the persistence of structured pattern, would require a pattern that is something over and above its constituents. The nihilist position, in its strict form, dissolves the Substance role into arrangements of underlying simples and denies that the arrangement composes anything further.

A clarification before the moves. The nihilist is not denying that the world contains the arrangements ordinarily called "chairs" and "tables." Van Inwagen and Sider both grant the arrangement-facts; what they deny is that the arrangements compose further objects. "Simples arranged chair-wise" describes a real configuration on every nihilist account; what it does not describe, on the strict version, is a chair as an additional ontological item. The question turns on whether the structural argument requires composite objects beyond the arrangements, or whether the arrangements themselves carry the structural roles. Three forms of the move press that question at three resolutions: the basic eliminativist version, Van Inwagen's organism-exception version, and Sider's strict version. Each reads the structural argument as requiring composite objects and replies by denying them. Each misreads what the argument requires.

*First.* The basic eliminativist move denies composition wholesale. There are no composite objects (chairs, tables, planets, organisms), only simples in various arrangements. The structural argument, in describing the persistence of configurations across time, has been describing composites the nihilist rules out. Without composites, no Φ; without Φ, the Triconditional fails.

The argument does not need composites in the sense the nihilist denies. What it needs is that the arrangements themselves instantiate the structural roles. A pattern of simples arranged chair-wise that persists across a temporal interval instantiates Φ at the level of the arrangement, whether or not the arrangement composes a further object called "the chair." Persistence is a feature of the pattern, not a posit beyond it. The nihilist who grants that the arrangement obtains, and obtains across time, has granted the structural role; what they have refused is the additional ontological commitment to a composite as a further item. The argument is neutral on that further item. T, S, and Φ specify what arrangements consist in, not what arrangements compose. Compositional nihilism leaves the structural roles where they are.

*Second.* Van Inwagen's organism exception holds that living things compose but artifacts and inanimate aggregates do not. The criterion is unity: the activities of an organism's parts are coordinated in service of the organism's life in a way that the parts of a chair are not coordinated in service of the chair. Living things therefore qualify as composites; chairs and tables do not. The structural argument, on this reading, gets purchase only where Van Inwagen's exception holds.

The criterion Van Inwagen invokes is itself Φ at the appropriate resolution. Causal persistence of a configuration across temporal change, where the configuration's persistence is constitutively maintained by its internal causal activity: that is what Substance names in the structural argument, and it is what Van Inwagen identifies as the mark of organic unity. The argument generalizes the criterion rather than restricting it. Any arrangement whose obtaining is constitutively maintained across time by its own causal activity instantiates Φ; the question is whether the maintenance is real, not whether the arrangement is biological. Crystalline lattices maintain themselves through electromagnetic binding; weather systems maintain themselves through fluid dynamics; the argument applies wherever maintenance obtains. Van Inwagen draws the line where the maintenance is most conspicuous; the argument follows the maintenance wherever it goes.

*Third.* Sider's strict version denies even Van Inwagen's exception. There are no composites at any level, organisms included; only simples in various arrangements, including the arrangements ordinarily described as living. The arrangement-facts obtain (Sider does not deny that simples are arranged organism-wise), but no further composite organism exists. The structural argument, on this version, must run entirely on arrangement-facts, without the resource of any composite bearer.

The recasting is the right one for the strict nihilist, and the reply is correspondingly cleaner. Arrangement-facts that obtain across time, with patterns maintained by causal activity among their constituents, instantiate the structural roles whether or not they compose further objects. The argument operates at the level of what arrangements consist in. Sider's strict version concedes the arrangement-facts; it denies the further composite. T, S, and Φ are specifications of what arrangement-facts must be like to be the kind of facts they are: temporally persistent, relationally distinct, causally maintained. The argument's necessity claim runs at the arrangement-fact level. Whether the additional composite is also there is a separate ontological question the structural argument leaves open. Sider's nihilism, taken at its strictest, is compatible with the structural argument: it constrains the inventory of composites without contesting the structure of arrangements. Sider's nihilism is only one of two commitments he brings to bear here; the other (his joint-carving structuralism, on which the live question is whether T, S, and Φ belong to the fundamental ideology rather than sit above a deeper structure) is the subject of [§4.4.7](<4.4.7 Sider's Structuralism.md>), where that question is engaged on its own terms.

A kindred move runs through priority monism (Schaffer 2010). Where the nihilist denies composites by eliminating them, the monist denies composites as fundamental by absorbing them into the cosmos: only the whole cosmos fundamentally exists, and the apparent composite objects are derivative aspects of it. The reply runs in the same direction. Whether the cosmos is fundamental and its parts derivative, or the simples are fundamental and the apparent composites eliminated, the structural argument operates at the level of the arrangements that obtain (at whatever ontological level the arrangements are located) and on the structural conditions any obtaining arrangement must instantiate. The composition question is orthogonal to the structural-role question. The same applies to the bundle/trope alternatives canvassed in [§4.3.10](<4.3.10 Bundle and Trope Theory.md>): those answers, like nihilism, address what the inventory contains rather than what the inventory's items must be like to obtain.

*What converges.* Each of the three forms misreads what the argument requires. The basic eliminativist move denies composites the argument does not need; the structural roles attach to the arrangements, not to the composites the arrangements may or may not constitute. Van Inwagen's organism-exception invokes a unity criterion that just is Φ at the level of organic maintenance; the argument generalizes the criterion to any arrangement constitutively maintained by causal activity. Sider's strict version concedes the arrangement-facts while denying the composites, and the arrangement-facts are exactly where the structural argument operates. Nihilism, at every resolution, leaves the structural roles where they are.

One clarification of scope is owed, because Van Inwagen's signature pressure is not compositional but modal-epistemic. His deeper question (how one knows that T, S, and Φ are *necessary* rather than merely pervasive, given how far that claim sits from the conceptual and near-by possibilities the modal faculty handles reliably) is not answered by the compositional reply above, and is not meant to be. That pressure is upstream of this section, and the book's answer to it is methodological rather than intuitive: the necessity verdict is claimed as the output of the derivation of §[§2.6](<2.6 Triconditionality of Nature.md>)–2.7, not of a modal intuition about distant scenarios, which is precisely the non-intuitive line Van Inwagen's own modal skepticism leaves open. This section discharges the compositional half of the Van Inwagen inheritance; the modal-epistemic half is engaged on its own terms at [§4.1.13](<4.1.13 Modal Epistemology and the Remoteness Objection.md>), and paid where the necessity is derived, not where composition is discussed.

What Van Inwagen saw clearly, and Sider sharpened, was that the modern compositional tradition had multiplied entities far past anything the world's structure demanded. The classical-mereology pedigree (from Leśniewski's plenitudinous parthood through Lewis's *Parts of Classes* to contemporary unrestricted-composition defenses) produced an inventory the nihilist was right to refuse on grounds of austerity. What the nihilist tradition has not always seen as clearly is that the world's structure does not consist in that inventory either. It consists in what arrangements (composite or not) must be like to obtain. The composition debate is real; it runs on a level the structural argument leaves open. Wherever simples are arranged in patterns that obtain across time, are distinct from other patterns, and are maintained by causal activity, T, S, and Φ are there. The argument is for the structure of what obtains, not for the inventory of what composes.


---

← [4.3.10 Bundle and Trope Theory](<4.3.10 Bundle and Trope Theory.md>) | [4.3.12 Haecceitism](<4.3.12 Haecceitism.md>) →
