Substantialist

Substantialist is a term used in philosophy to denote a defender of substance-based ontology. Substances are typically conceived as stable, underlying bearers of properties that exist independently of their attributes and relations. Substantialist theories hold that statements about objects ultimately refer to enduring substrata or substances rather than to mere bundles of properties or to relational structures.

Historically, substantialism has roots in Aristotle's account of substances as the primary category of being. In medieval scholastic thought, it was developed with distinctions between matter and form. In the early modern period, Descartes posited two kinds of substances (res extensa and res cogitans); Spinoza proposed a single, all-encompassing substance. Kant challenged the knowability of substances as things-in-themselves, a critique that continues to influence contemporary debates about persistence, identity, and ontological commitment.

In contemporary metaphysics, substantialists defend the idea that substances are fundamental for explaining persistence, causation, and the nature of objects, while opponents argue that a bundle theory, relational theory, or other ontologies can account for these phenomena without commitment to underlying substrata. The debate often centers on how change, diversity, and similarity are grounded in a supposed enduring entity.

The term is also encountered in the philosophy of space and time, where substantivalists argue that space-time points exist independently of physical stuff; however, in general usage, substantialist more often refers to a broad commitment to substance-based ontology rather than to space-time debates.

See also: substance theory, bundle theory, ontology, persistence, essentialism.