Substance personalism is the philosophical position that the person is a substance — an independently existing spiritual being that cannot be reduced to its properties, functions, or acts. This view is held, within the tradition of realist phenomenology and Thomism, above all by Edith Stein, Josef Seifert, and Robert Spaemann. Their shared fundamental thought: the person is a someone, not merely a something — and this being-someone is grounded in a substantial being that precedes all acts, faculties, and states and that bears them.
The decisive advantage of substance personalism becomes apparent where act personalism reaches its limits: in the question of the identity of the person over time. Whoever understands the person merely as the enacted nexus of their acts cannot explain why the sleeping, unconscious, or dementia-stricken person remains the same person. Substance personalism can: the person remains identical because their being does not depend on their current enactments. The person is before they act, and they remain even when they can no longer act. The principle agere sequitur esse — acting follows being — captures this connection precisely.
Substance personalism presupposes the concept of substance as it was developed in the Aristotelian-Thomistic tradition. Substance here does not mean rigidity or self-enclosure, but independent self-subsistence — the precondition for the person’s ability to communicate, to know, and to love. Only one who is at home in themselves can go out of themselves. The substance-ontological concept of person develops this insight systematically.
Sources: Generated by querying the Personhood ontology. Bexten 2017, ch. 2 (substance-ontological concept of person) and ch. 6 (comparison of the concepts of person).
Further sources:
- Spaemann, Robert (1996): Personen. Versuche über den Unterschied zwischen „etwas” und „jemand”. Stuttgart: Klett-Cotta. (Eng.: Persons. The Difference between “Someone” and “Something”, Oxford: Oxford University Press, 2006.)
- Thomas Aquinas: Summa theologiae, I, q. 29 (De personis divinis).
- Boethius: Liber de persona et duabus naturis (ca. 512).