T, S, and Φ are not three independent conditions that happen to co-occur. They *are* one structure read along three axes, and each, fully unpacked, reveals the others as its own internal requirements rather than as external correlates.

**Structure.** *A structure is not a thing alongside the things it structures. It is the ordered set of relations, constraints, and roles by which anything is intelligible as a thing, field, event, or configuration at all. In this book, structure names Reality under its necessary ordering: Temporality, Spatiality, and Physicality together as the conditions any possible item must already exhibit to be anything determinate. Structure therefore does not exist instead of things, and it is not imposed on a prior unstructured stuff. It is what any existing thing must already have in order to exist as anything at all.*

Temporality is not a finite thing, Spatiality is not a locational thing, Physicality is not a material thing. They *are* what finite things, locational things, and material things *consist in*.

T, S, and Φ are introduced at [§1.4](<1.4 Three Conditions.md>) and derived at §[§2.4.5](<2.4.5 Forward Conditional.md>)–2.4.10. If change is genuinely possible, the Conditions are already in play ([§2.4](<2.4 Structural Requirement.md>)); [§2.6](<2.6 Triconditionality of Nature.md>) turns on the converse: if the Conditions are instantiated, change is possible.

The consequence is immediate: these are not three necessities that travel together. They *are* one necessity seen from three sides.[^2-6-1-three-conditions-one-nature-ch4]

*The realizer move.* Every relation this chapter names (directed succession, genuine distinctness, causal transmission, exclusive occupancy, persistence, identity through change) admits a thin reading on which it reduces to labeling, self-relation, or coordinate notation, and a real reading on which it requires structural machinery to distinguish it from its deflationary mimic.

The Conditions T, S, and Φ are the realizers of each other's real readings. To say T ↔ (S ∧ Φ) is to say: the real reading of directed succession requires both relational extension and persistent bearing, and the conjunction of those two requires directed succession. The same holds for S ↔ (T ∧ Φ) and Φ ↔ (T ∧ S). Three triconditionals, one move, pivoted on each of the three terms in turn.

Succession alone demands an interval to cross and a medium to carry it. Extension alone demands a direction and a being. Persistence alone demands a direction to persist through and an interval to persist across. Each Condition, attempted in isolation, summons the other two as what the attempt consists in.

The triconditionals yield the *Mutual Containment Result*, gathered formally at [§2.6.5](<2.6.5 Mutual Containment.md>): lacking any one Condition entails lacking all three.

The physical confirmations of these relations (relativistic spacetime unification, conservation laws, thermodynamic asymmetry) are addressed in Chapter 7 as empirical expressions of what is established analytically here.

*A clarification on idiom.* The thin/real reading distinction throughout this section tracks a structural-functional distinction (what directed succession *requires* as a structural matter), not a hyperintensional-essence distinction (what directed succession is in its essence prior to modality). 'Internal requirements' names structural co-requirements of the primitive modal field, not essence-prior real definitions in Fine's sense. Whether this structural-functional use of 'consists in' and 'requires' can be kept stable against Fine's pressure (that any such structural identity just is a real definition under a different label) is the question addressed at [§4.1.10](<4.1.10 The Source of Possibility.md>).

First: whether succession can stand without extension.

[^2-6-1-three-conditions-one-nature-ch4]: The three-Conditions-one-Nature framing (that T, S, and Φ are one structural fact read along three axes rather than three independent conditions) is engaged in Chapter 4. The closest contemporary ally is structural realism (Ladyman & Ross, French), which nonetheless diverges on what the structure consists in ([§4.3.9](<4.3.9 Structural Realism.md>)). Sider's structuralism ([§4.4.7](<4.4.7 Sider's Structuralism.md>)), bundle theory and tropes on the compose-by-relation picture ([§4.3.10](<4.3.10 Bundle and Trope Theory.md>)), and mereological nihilism on whether there is anything for the three to be conditions of ([§4.3.11](<4.3.11 Mereological Nihilism.md>)) press from their own directions, and Quine's anti-distinction pressure asks whether the three pivots name a single fact under three readings or three independent facts ([§4.1.6](<4.1.6 Quinean Modal Skepticism.md>)).


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← [2.6 Triconditionality of Nature](<2.6 Triconditionality of Nature.md>) | [2.6.2 Succession's Two Conditions](<2.6.2 Succession's Two Conditions.md>) →
