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Every cell in my body is replaced every seven years, so am I even the same person?

Baraka Mwakyusa Contributor
· 4 replies
Personal identityAnalyticBuddhistModern EuropeanDerek ParfitJohn LockeNagasena#memory#personal-identity#responsibility#seven-year-myth
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Its coordinates: 1.3.2 Personal Identity

At Sunday lunch my uncle reminded me that I borrowed 20,000 shillings from him when I was fifteen. I said, as a joke, that every cell in my body has been replaced since then, so the boy who borrowed it is gone and the debt went with him.

He laughed, but then my cousin asked if it was actually true, and nobody knew.

So, two questions from someone who has never studied this:

  1. Is the seven-year thing true?
  2. If it were, would it mean I'm not the same person? What do philosophers say makes someone the same person over time?

(I will probably pay the uncle either way. But I would like to know whether I have to.)

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4 answers

  1. Rowena Abellana

    Fellow

    First the biology: the seven-year figure is a myth, or at least far too tidy. Cells turn over at very different rates. Some, like most of the neurons in your cerebral cortex and the cells at the centre of the lens of your eye, stay with you for life. So the premise fails before the philosophy starts.

    But suppose it were true. There are three main answers:

    • The body view: you are the same person if you are the same living organism, which stays the same even as its matter changes, the way a river stays a river.
    • Locke's view: what makes you the same person is consciousness reaching back to past actions, especially memory. He imagines a prince's consciousness waking in a cobbler's body and says the person goes with the consciousness. He also says "person" is a forensic term, meaning it exists for responsibility, praise and blame. So, by Locke, if you remember borrowing the money, the debt is yours.
    • Parfit: identity is not what matters. What matters is psychological connection and continuity, which come in degrees. Your fifteen-year-old self is strongly connected to you. Pay your uncle.
  2. Gerrit Venter

    Fellow

    A rugby man's version of the body view. I coached the same school under-16s for thirty years. Not one player stayed; every year they were new boys. And yet it was the same team, with the same songs, the same grudges against the same rival school, the same debts in the tuck shop.

    What kept it the same was a continuing practice, not continuing material. I suspect people are a bit like that too, only with more memory.

  3. Nuwan Perera

    Contributor

    In Sri Lanka we have an older version of this question. In the Questions of King Milinda, the king asks the monk Nāgasena whether someone who is reborn is the same person or another. Nāgasena says: neither the same nor another. He gives the example of a lamp burning through the night. The flame in the last watch is not the flame of the first watch, but it is not a different lamp either.

    My father used to say the same about debts. The flame still owes the oil.

  4. Baraka Mwakyusa

    Contributor

    So the cells argument fails twice: the fact is wrong, and even if it were right, Locke would ask whether I remember borrowing the money. I remember very well. It was for a football.

    Gerrit and Nuwan, I like the team and the lamp. I will tell my uncle he lent the money to a flame, and the flame will pay at the end of the month.