Notes on Types of Personal Identity by Katherine Hawley

Personal identity refers to the concepts that determine what it means to be the same person over time.
Questions arise about continuity in identity, such as: What makes a person the same as they were years ago? Is it the body, memories, personality, or something else?
Understanding personal identity involves addressing another question: What does it mean for something to exist at more than one moment?
This article will explore three potential answers to the question of what constitutes personal identity, moving towards a particular interpretation that may offer clarity.

One perspective argues that identity is tied to the physical body: being the same person is contingent on having the same body as in childhood.
This raises further inquiries about what constitutes the same body over time.
Example: Consider a hypothetical scenario where you are near death but your brain is intact. If your brain is transplanted into another body (e.g., Sam's), you may retain memories and personality traits despite inhabiting a different body.
This suggests that body identity is neither necessary nor sufficient for personal identity, as evidenced by the fact that Sam's body can continue to live even after he is not alive anymore.

Some reject the body perspective, asserting that identity is a matter of having the same brain.
The argument here maintains a closer connection to brain identity than physical body identity.
If another person's brain (Sam’s) contains your mental characteristics after a transfer, this raises questions about whether the identity persists.
Variation of the Argument: If your brain is wiped and replaced with memories and traits into Sam's body, you continue your existence with all personal attributes intact. This emphasizes that the specific biological substrate (the brain) may be less essential than the continuity of the psychological traits.

The third answer focuses on psychological continuity through memory and mental connections rather than physical entities. This answer holds that personal identity relies on a connection between past and future psychological states.
This psychological continuity is not limited to mere memories but includes traits, preferences, and consciousness as well.

Personal identity is crucial for individuals as it pertains to regrets, pride in past actions, and the concept of personal responsibility regarding past actions. For others, knowing who someone was is vital for accountability and property rights.
In philosophical discourse, personal identity is also essential when discussing concepts of reincarnation or bodily resurrection.

There are two fundamental questions in personal identity:
1. Constitutive Criterion: What constitutes personal identity? What exactly is personal identity?
2. Epistemic Criterion: How can we recognize the same person over time? How can we determine if a current individual is the same as they were in the past?
Hawley expresses interest in constitutive criteria, aiming at understanding the essence of personal identity.

David Lewis states, "Identity is an utterly unproblematic notion. Everything is identical to itself. Nothing is identical to anything else."
This simplistic view of identity contrasts with the complexity found in identity over time.

Some philosophers argue against the traditional view by suggesting that identity over time includes a temporal dimension. Objects, including people, can be viewed as four-dimensional, incorporating their existence across time as well as space.
Analogy: Just as you can view parts of a street at different moments, different temporal aspects of a person can reflect different characteristics of the same individual over time.
Philosophers who adopt this view see identity issues as concerning whether temporal segments (parts) belong to the same entity, indicating that the green banana (yesterday) and yellow banana (today) might not be identical but parts of the same entity extending through time.

The three-dimensional view holds that identity remains intact over time despite different appearances or states.
In contrast, the four-dimensional perspective emphasizes the existence of different temporal parts, questioning the notion of strict identity over time.

A third perspective, described by Hawley as the 'happy-medium' theory, posits that identity over time can be understood as type-identity rather than strict identity.
Here, two different instances of a person over time share the same type but are not the identical entities. For example, the banana at two different moments is not the same fruit but is of the same type.

Bernard Williams presented issues regarding criteria of identity in cases where a person’s identity could apparently duplicate, causing them to be identical to multiple future beings post-transplant.
Hypothetical Example: Imagine that half of a brain can survive independently in separate bodies. Which becomes 'you'? If both or neither, are you dead or still existing? This highlights potential conflicts in the criteria of personal identity.

Wright's puzzle illustrates that one person cannot be identical to two different individuals post-splitting scenario. The four potential outcomes of this dilemma present challenges that dissolve conventional definitions of identity post-duplication.
One view is that only one entity is you, but this delineation feels arbitrary.
Alternatively, it proposes that two entities are the same, contradicting the principle of individual identity.

Derek Parfit's perspective suggests that 'identity is not what matters.' He emphasizes that the future outcomes of personality traits and psychological continuity are what are significant, rather than strict identity.
Parfit’s views indicate that identity relieves pressure off existential concerns concerning future selves, as future iterations of personality may continue despite a lack of identical continuity.

The three-dimensional perspective maintains that entities can retain identity through changes made over time.
The four-dimensional perspective posits that physical and psychological characteristics change at different intervals in time.
The happy-medium view merges these two concepts to advocate that, while dynamic, identity remains consistent in the type.

In discussing personal identity, it’s crucial to refine our understanding of identity itself and to recognize that the matter of identity overlaps with personhood from a perspective that minimizes concern about the physical assumptions.

Recognition is given to Sam Inglis, Nick Jardine, Joel Katzav, James Ladyman, Peter Lipton, Eric Olson, and Peter Smith for their contributions to the discourse surrounding personal identity.

Lewis, David (1976) Survival and Identity in Rorty's compilation.
Parfit, Derek (1971) Personal Identity in The Philosophical Review.
Parfit, Derek (1984) Reasons and Persons, Oxford University Press.
Perry, John ed. (1975) Personal Identity, University of California Press.
Williams, Bernard (1956-57) Personal Identity and Individuation, Proceedings of the Aristotelian Society.