Parfit on Personal 'Identity'

The problem of personal identity is the question about how we define a person.  In other words, what makes me me?  How do we decide if there is some person who is the same person as me?  Locke answers this problem by saying that personal identity consists of autobiographical memories.  Reid shows that this theory will violate the transitivity of identity.  Parfit's contribution to the literature on the problem of personal identity is to note that strict numerical identity might not be the appropriate concept.  Rather, he talks about survival.  The question of whether you survive is the same question as whether there is some person who is you.  In the links below, I discuss the difference between identity and survival in more detail.

Parfit on PID.

Identity vs. Survival.

Locke on Living Things

"That being then one plant which has such an organization of parts in one coherent body, partaking of one common life, it continues to be the same plant as long as it partakes of the same life, though that life be communicated to new particles of matter vitally united to the living plant, in a like continued organization conformable to that sort of plants." (Bk. II, Ch. XXVII, sect. 4)

In the above passage, Locke explains that the identity of a plant is determined by the fact that a plant participates in 'one common life' with 'an organization of parts' in one body.  Even though the life is 'communicated to new particles of matter', these new particles are 'vitally united' to the plant.  Vital here means not only essential but also related to the life of the plant (c.f., vital signs, vitality).

Even a cell is a living thing with an organization of parts.  The different parts of the cell each have a function in preserving and perpetuating the life of the cell.  Although the specific particles or atoms that make up the cell may change over time, the life is a continuous one.  The body may exchange some particles for others, but it remains coherent.

Pfizz #1 and Answers

1. What is the problem of personal identity?

How can we say that I am the same person now as I was when I was younger? What does it mean to be a person?

2. What is Locke's solution to the problem of personal identity?

Locke says that the identity of a person is constituted by conscious awareness of autobiographical memories. You are whoever you remember being and whatever you remember doing.

3. Explain the brave officer example and how it proves Locke wrong.

A person, P, may remember an event, A, during the time of another event, B. During event C, he remembers event B but not event A. If memory constitutes personal identity, then A = B and B = C (since at B he remembers A and at C he remembers B). By the law of transitivity of identity, C should be identical to A. Yet this would violate Locke's criterion for personal identity, because at C, he does not remember A.  

4. How did Parfit clarify the problem of personal identity?

Parfit clarifies that theories about what a person is that lead to a violation of the transitivity of identity are not bad simply because they violate the transitivity of identity. Parfit says that when we talk about a person being the same as me, we're not talking about strict numerical identity. Rather, we're talking about something else: survival. Survival requires neither a 1:1 ratio nor an all-or-nothing categorization.  

Identity, Locke and Objections

Identity can be expressed in a few different formulas.  The reflexivity of identity can be exprssed with "A = A".  In regular language, a thing is the same with itself.  The symmetry of identity is expressed as "If A = B, then B = A".  Meaning that if what you thought were two things are actually identical, then they must be exactly the same in every regard.  The transitivity of identity can be expressed as "If A = B and B = C, then A = C."  In other words, if one thing is identical to two things, then those other two things must also be identical to each other.

A famous objection to Locke comes from a violation of the third expression of identity.  In this blog post, I discuss Thomas Reid's objections to Locke, including the one that is based on a violation of the transitivity of identity.

Tabula Rasa: Some Context for Locke

To provide some context for Locke's theory of personal identity, it may help to know what he thought about out minds and how they work.  Locke thought that everyone is born with a 'blank slate' for a mind.  This means that our minds are empty when we are born.  Every experience and perception creates an impression on the mind, leaving behind information and memories.  So you can see, if our minds (finite mental substances, i.e. souls) are empty without any memories, it makes sense then that awareness of memories is what makes personal identity.

Different Thing, Different Criterion for Identity

In Locke's An Essay Concerning Human Understanding, Locke contrasts human personal identity with identity of different kinds of things.  He begins with a general principle of identity: something is identical only to itself, and it is impossible for two things to exist in the same place at the same time.  From this, we get a criterion for the identity of bodies, or physical objects.  Physical objects stay the same so long as they stay the same combination of atoms.  When something (mass, atoms, substance) is added to or removed from a physical body, then that body changes and is no longer identical to a past version of itself.  Bodies are identical to themselves insofar as they continue to be the same collection of atoms.  Locke notes that this criterion does not apply to living things like plants.  An oak tree begins as an acorn, grows into a tree and may eventually be cut down.  We say it is the same oak tree even though the atoms and particles that make up that oak tree have changed.  Then what is the criterion for the personal identity of a tree?  Well, the atoms of the tree may change over time, but the tree maintains an organization of its parts.  The tree's parts are organized in a way to contribute to its nourishment and to the continuation of its life.  Simply put, plants are organized living bodies.  So long as a tree maintains this organization throughout the course of its life, then it is the same tree (even though the atoms that compose the tree have changed many times).  Animals, brutes (yes, this is a racist term applied to non-European, non-"civilized" humans) and machines are all like plants insofar as they are all bodies that are organized for a certain end (goal).  In animals and brutes, we can see the movement that results from their organizing processes; in plants we cannot.  Machines differ from animals and brutes insofar as machines move only when acted upon by external forces.  Animals, however, are the source of their own motion.  Still, none of these distinctions has yet clarified the criterion for personal identity of humans; that's because that what makes a person identical to himself or herself is something different and unique to human beings: a soul.  Specifically, Locke understands 'soul' to refer to our conscious awareness of our thoughts, experiences, perceptions and actions.  Human personal identity depends on our awareness of past events in our lives.  Our identity is made up of the things we remember thinking and doing.

Locke on Personal Identity

What is personal identity?  Generally speaking, personal identity is what makes a person the same person throughout his or her life.

Locke provides a psychological criterion for personal identity.  Specifically, he thinks that your personal identity is constituted by your awareness of memories.  Your personal identity extends as far back as your memories go back.  Insofar as you are aware of a memory in your past, it is part of your identity.

So, If Arnold Schwarzenegger, former Governor of CA, remembers being in The Terminator, winning the Mr. Universe competition and growing up as a young boy in Thal, Graz, Austria, then he is the same person.  If, however, he does not remember being a young boy in Thal who slept in a tiny bed and used a pit toilet, then those experiences are no longer part of his personal identity.

Indeed, if we take awareness of memories to be constitutive of personal identity, then anything we forget is no longer part of our personal identity.