Substance ontology is the ontological framework in which the being of the person is understood as substance — as an independently existing spiritual entity that bears the ground of its being and its identity within itself. It stands in opposition to ontologies that reduce the entity to properties, functions, relations, or events.
The substance-ontological tradition begins with Aristotle, who determines substance (οὐσία) as the first of beings: that which is not predicated of another, but of which other things are predicated (Metaphysics VII). Thomas Aquinas deepens this approach by conceiving substance as ens per se subsistens — an entity that subsists through itself, not as a property of another. Boethius’ famous definition of the person — naturae rationalis individua substantia — applies substance ontology to the debate over the concept of person: the person is an individual substance of a rational nature.
In realist phenomenology, substance ontology is carried forward by Edith Stein, Josef Seifert, and Robert Spaemann. In Finite and Eternal Being, Stein joins the Thomistic doctrine of substance to the phenomenological method. In Sein und Wesen, Seifert develops an independent substance-ontological position. In Persons, Spaemann shows that the distinction between someone and something presupposes a substance-ontological foundation.
For the debate over the concept of person, substance ontology is decisive because it explains why the person remains the same even when she performs no spiritual acts — in sleep, in coma, in dementia. The substance-ontological concept of person and the substance-ontological-relational concept of person are grounded in this framework.
Sources: Generated by querying the Personhood ontology.
Further sources:
- Aristotle: Metaphysics, Book VII (Ζ). The Complete Works of Aristotle, ed. Jonathan Barnes. Princeton: Princeton University Press, 1984.
- Aquinas, Thomas: Summa Theologiae, I, q. 29 (On the divine persons).
- Boethius: Liber de persona et duabus naturis (ca. 512). The Theological Tractates, transl. H. F. Stewart, E. K. Rand, and S. J. Tester. Cambridge, MA: Harvard University Press (Loeb Classical Library), 1973.
- Spaemann, Robert: Persons. The Difference between “Someone” and “Something”. Transl. Oliver O’Donovan. Oxford: Oxford University Press, 2006.
- Seifert, Josef (1996): Sein und Wesen. Heidelberg: Winter (German).