In philosophy, the matter of personal identity deals with such questions as, "What makes it true that a person at one time is the same thing as a person at another time?" or "What kinds of things are we persons?" The term "identity" in "personal identity" refers to "numerical identity," where saying that X and Y are numerically identical just means that X and Y are the same thing. Personal identity is not the same as personality, though some theories of personal identity maintain that continuity of personality may be required for one to persist through time. In relation to answer questions about persistence, such as under what conditions a person does or does not continue to exist, contemporary philosophers often seek to first answer questions about what sort of things we are, most fundamentally. Many people claim we are animals, or organisms, but many others strongly believe that no person can exist without mental traits, such as consciousness. Since an organism can exist without consciousness, both these views cannot be true (if we are organisms we can exist without being conscious; but if we can't exist without consciousness, we are not organisms). Thus, in order to determine whether certain features (such as consciousness) are crucial to a person's continued existence, it may be important to first ask what sort of things we are.
Generally, personal identity is the unique numerical identity of a person in the course of time. That is, the necessary and sufficient conditions under which a person at one time and a person at another time can be said to be the same person, persisting through time;
In contemporary metaphysics, the matter of personal identity is referred to as the diachronic problem of personal identity. The synchronic problem concerns the question of: What features and traits characterize a person at a given time. In Continental philosophy and in Analytic philosophy, enquiry to the nature of Identity is common. Continental philosophy deals with conceptually maintaining identity when confronted by different philosophic propositions, postulates, and presuppositions about the world and its nature.
- 2.3: Removing “identity” from “persons”- Derek Parfit
- Reasons and Persons is a philosophical work by Derek Parfit, first published in 1984. It focuses on ethics, rationality and personal identity. His views on personal identity transformed how it is understood and used in philosophy, especially ethics.
- 2.4: The Ship of Theseus
- The ship of Theseus, also known as Theseus' paradox, is a thought experiment that raises the question of whether an object that has had all of its components replaced remains fundamentally the same object. The paradox is most notably recorded by Plutarch in Life of Theseus from the late first century. Plutarch asked whether a ship that had been restored by replacing every single wooden part remained the same ship.