Identity denotes the selfsameness of the person across time: the same person who existed yesterday exists today. This diachronic unity is not a construction of consciousness, but is grounded in the substance-ontological being of the person.
The Problem of Diachronic Identity
The empirical-functionalist concept of person cannot explain diachronic identity: if personhood is constituted by actually exercised self-consciousness, the person disintegrates into a sequence of temporally limited states of consciousness. David Hume reduces the self to a bundle of perceptions; Derek Parfit declares personal identity an illusion.
The diachronic identity objection is directed against this position: only a substance-ontological subject can bear the unity of the person across time.
Substance-Ontological Solution
The person is identical with itself because it is a spiritual substance that remains the same through the change of its states. Identity is not the product of memory (Locke), but its presupposition: one can remember something only if one is the same subject that had the experience.
Sources: Generated by querying the Personhood ontology.
Further sources:
- Spaemann, Robert: Persons. The Difference between ‘Someone’ and ‘Something’, transl. Oliver O’Donovan. Oxford: Oxford University Press, 2006.
- Thomas Aquinas: Summa Theologiae, I, q. 29 (On the divine persons). Transl. Fathers of the English Dominican Province. New York: Benziger Bros., 1947.
- Boethius: Liber de persona et duabus naturis (Contra Eutychen et Nestorium, c. 512). In: The Theological Tractates, transl. H. F. Stewart, E. K. Rand & S. J. Tester. Cambridge, MA: Harvard University Press (Loeb Classical Library), 1973.