Haecceitism holds that the facts about which individual is which are not exhausted by the qualitative and relational facts: two situations can agree on every qualitative and relational property and still differ over which individual is which. Adams's *Primitive Thisness and Primitive Identity* (1979) gives the position its canonical analytic statement: a thisness is the non-qualitative property of being this very individual, grounding numerical identity prior to and independently of any qualitative or relational characterization. The motivating case is older: Black's "The Identity of Indiscernibles" (1952) describes a symmetric universe of two qualitatively indiscernible iron spheres, two and not one, with nothing qualitative to tell them apart. Lewis's *On the Plurality of Worlds* (1986) is the locus of the contemporary debate, rejecting non-qualitative differences between worlds in favor of a counterpart-theoretic treatment, on which an individual figures in other possible situations not literally but through its qualitatively closest counterparts there, so that qualitative character fixes all there is to fix. The subsequent literature (Skow 2008) separates a deflationary form, which grants haecceitistic possibilities without positing primitive thisnesses, from the robust Adamsian form, which grounds them in genuine non-qualitative properties. What unites the family is the refusal to reduce individuation to qualitative or relational structure.

The position bears on the spatial Condition directly. Positional distinctness is grounded in relational extension at [§2.4.7](<2.4.7 Distinction Requires Spatiality.md>), which states the load-bearing Constitutive Premise: genuine non-identity at the positional level just *is* relational non-identity, distinctness constituted by a traversable interval, not by intrinsic difference. Haecceitism is the most direct denial available. If a primitive thisness grounds the distinctness of two items independently of any relation between them, then distinctness need not be relational, and the premise on which the derivation of Spatiality turns is false. The relationalist pressure on that same premise, Dasgupta's *Individuals: An Essay in Revisionary Metaphysics* (2009), which [§2.4.7](<2.4.7 Distinction Requires Spatiality.md>) already engages, pushes from below, holding individuals to be less fundamental than structure; haecceitism presses from above, holding thisnesses to be more fundamental than any structure they enter into.

Grant the position at full strength. Haecceitism may well be the correct account of individuation as such. Black's symmetric universe is a real difficulty for any view that grounds all numerical distinctness in qualitative difference, and the obvious relational repair (distinguishing the spheres by their distances from things) cannot break a symmetry in which every relational description one sphere satisfies is satisfied by the other. The concession should be larger still. The consideration sometimes pressed against the haecceitist (that even a primitive thisness must be picked out as *this* rather than *that*, and so already trades on a contrast) does not by itself settle the matter, because how a thisness must be *referred to* is a fact about representation, not about what the thisness *is*. A haecceitist who locates the individuating work in the order of being while assigning the contrast to the order of description has not thereby been refuted. The reply does not run through that bridge.

What the structural argument requires is narrower than the thesis the haecceitist denies. The derivation does not need every numerical distinctness to be relational; it needs the distinctness that *change* crosses to be relational. Spatiality is the Condition movement presupposes, and movement is displacement across an interval: a crossing. The distinctness at issue in [§2.4.7](<2.4.7 Distinction Requires Spatiality.md>) is therefore positional distinctness specifically: the non-identity a displacement traverses. Primitive thisness, whatever else it grounds, does not by itself supply an interval to cross. A thisness delivers a label (this individual, not that one), and a label is not a distance. Two items distinct in thisness alone, with no relational extension between them, are non-identical in just the way red is non-identical to blue: distinct, with nothing between them that anything could move across. That is exactly the line [§2.4.7](<2.4.7 Distinction Requires Spatiality.md>) draws between a difference of contents or names and a distinctness of positions. The haecceitist's primitive grounds *that* the items are two; it does not make their twoness *positional*.

The flagship case confirms the premise rather than threatening it. Black's two spheres are positionally distinct, and they are positionally distinct because a relational interval separates them: a distance something could cross, the very feature the Constitutive Premise names. What the case withholds is a *qualitative* ground of distinctness; it does not withhold the interval. The distance in Black's original case suffices for positional distinctness while leaving the spheres qualitatively indiscernible. It does not prove that distance is necessary for numerical plurality: a robust haecceitist may posit co-located indiscernibles. Black's universe is therefore compatible with relational individuation of position, but it does not by itself refute primitive thisness. The haecceitist is right that the distinctness is not qualitative, and right that no description breaks the symmetry; what follows is that the distinctness is relational-extensional, which is what Spatiality is.

A defender might press the harder case: two indiscernibles with no interval between them, co-located, or differing only in which is which across possible worlds. If such distinctness is genuine, it is distinctness without a crossable interval, and the premise fails. The case divides, and neither half reaches the spatial claim. Where the two are co-located with no interval between them, there is nothing a displacement could traverse from the one to the other; whatever makes them two, it is not a positional distinctness, and the argument never held that primitive thisness fails to ground individuation of a non-positional kind. Where the distinctness is the trans-world question of which individual is which, it concerns identity across worlds, not the distinctness of positions within Reality, and the spatial claim is about the latter. Neither half exhibits a positional distinctness across which nothing could move: the one thing the Constitutive Premise rules out.

*What converges.* The robust Adamsian thisness, the deflationary haecceitistic possibility, and Black's symmetric universe all press one point: that distinctness is not qualitative. The structural argument grants it. What none of them supplies is a positional distinctness without a crossable interval, and that, not the reduction of all individuation to relation, is what the Constitutive Premise asserts. Where a haecceitist case carries an interval, it instantiates the relational extension Spatiality names; where it carries none, it is individuation of another kind, which the argument leaves untouched. Haecceitism constrains what grounds identity; it does not displace what grounds position. Like bundle theory and mereological nihilism ([§4.3.10](<4.3.10 Bundle and Trope Theory.md>), [§4.3.11](<4.3.11 Mereological Nihilism.md>)), it answers a question about the inventory of individuals, not the question of what an interval must be for something to cross it.


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← [4.3.11 Mereological Nihilism](<4.3.11 Mereological Nihilism.md>) | [4.4 Modal Variants and Extensions](<4.4 Modal Variants and Extensions.md>) →
