The conceptual audit developed in this paper has three components: a semantic audit, an empirical audit, and a metaphysical audit. Together, these components support the Ontological Necessity Criterion (ONC), which evaluates when representational indispensability justifies ontological commitment. This section introduces ONC and clarifies how it differs from existing approaches, particularly spacetime functionalism.
3.1 Representational Indispensability and Ontological Commitment
Temporal and spatiotemporal vocabulary is indispensable for expressing dynamical relations. Proper-time intervals, coordinate assignments, and geometric structures are required to represent physical processes. But indispensability for representation does not, by itself, justify ontological commitment. Many indispensable representational tools – gauge potentials, coordinate systems, phase-space parameters – do not correspond to fundamental entities. The methodological question is therefore: What empirical or explanatory work would require positing a temporal or spatiotemporal entity as an additional ontological constituent?
This question motivates ONC.
3.2 The Ontological Necessity Criterion (ONC)
The Ontological Necessity Criterion states: A representational posit is ontologically necessary only if removing it leaves empirical or explanatory content unaccounted for. The criterion is deliberately modest. It does not claim that temporal or spatiotemporal entities never perform irreducible work. It claims only that such work must be demonstrated rather than assumed. ONC is designed to identify the additional premise required to move from temporal representation to temporal ontology. This premise is often left implicit in arguments for the fundamentality of time or spacetime.
Two clarifications are needed if the criterion is not to be misread. First, “change and relational structure” is not restricted to relations among material clocks or material events. It includes whatever physical states, relations, and dynamics the theory actually employs. If a metric-field realist is right that gravitational degrees of freedom, vacuum curvature, or radiative structure belong to that inventory, those structures count as part of the relational and dynamical content against which ONC is applied. Second, ONC then asks a narrower question: after those states, relations, and dynamics have been specified, does anything further—a temporal substance, a container, a flowing entity, or spacetime understood as an additional constituent over and above that structure—still make an irreducible empirical or explanatory contribution? Convenience of temporal vocabulary is not such a contribution. A residual difference in prediction or explanation would be.
3.3 ONC and the Conceptual Audit
The conceptual audit supports ONC in three ways:
– Semantic audit: identifies how polysemy, metaphor, indexicality, and reification enable unlicensed transitions from representational claims to ontological ones.
– Empirical audit: shows that empirical evidence typically constrains physical processes and relations, not temporal entities.
– Metaphysical audit: clarifies when explanatory roles attributed to time or spacetime can be discharged by change and relational structure.
Together, these audits provide the evidential and conceptual basis for ONC.
3.4 ONC and Spacetime Functionalism (Lam & Wuthrich 2018)
Spacetime functionalism begins by asking which roles associated with spacetime are required for the empirical phenomena described by physics and whether those roles can be realized by structures that are not themselves spatiotemporal. ONC takes the next step in the argument rather than competing with that reconstruction. The distinction can be stated as follows: Functionalism asks: what roles must be played, and what can play them? ONC asks: once those roles have been recovered, does the role-filler itself make an irreducible empirical or explanatory contribution?
Consider clock readings and inertial structure. A functionalist analysis can seek a structure that reproduces the relevant clock behaviour and inertial effects without treating spacetime as fundamental. If the recovery succeeds, a straightforward inference to fundamental spacetime is blocked. ONC then asks a different question: is there some residual phenomenon, prediction, or explanation that remains unaccounted for unless the role-filler is itself added to the ontology? Here “residual” has a specific methodological meaning. It is not whatever is described more conveniently using temporal or geometric vocabulary. It is an empirical or explanatory difference that survives after the relevant physical states, relations, and dynamics have been specified. If no such residue can be identified, representational indispensability does not by itself establish ontological necessity. If such a residue can be identified, ONC leaves room for the corresponding ontological posit. ONC therefore sharpens rather than displaces spacetime functionalism. Functional recovery addresses how the relevant roles can be realised; ONC makes explicit the further burden of showing why the realiser must itself be an additional constituent of reality.
