Wednesday, February 2, 2011

The Ship of Theseus a.k.a. Grandfather's Axe

There's an old philosophical puzzle. Suppose you have a wooden boat. You notice some of the planks are getting rotten, so you replace them. Is it still the same boat? As time goes on, you replace the planks one by one, until every single plank making the boat has been replaced. Is it still the same boat?

Alternatively, your grandfather's axe is a family heirloom. But when your father got it, he replaced the head, and when you got it, you replaced the handle. Is it still the same axe?

I posit that identity cannot be determined by the identities of the constituent parts.

First, I'll assume that identity is something that can be discerned - that is it's something that can be determined by observation. Intuitively, this makes sense. If you see two boats, you can distinguish them by how they look, even if they switch positions, or change by small amounts. Even if you have two boats made the same, there will be minute differences that can distinguish them. And the same with the planks. You can tell two planks apart.

But the fundamental constituents of matter have no such identity. An electron is an electron is an electron. All electrons are indistinguishable, and provably so. If you had an electron, and you put it in a box full of other electrons, it would not be possible to find your initial electron again. In fact, there isn't such a thing. Initially, there was one electron in your hand, and many electrons in your box. Then there were many+1 electrons in your box. The one electron cannot be uniquely tracked. It has no identity.

What this means is that if you have, say, a hydrogen atom, and then instantaneously swap out the electron with a different one... Then nothing has changed. Nothing has been done. If that hydrogen atom had an identity, it could not have changed, even if every single subatomic particle in it had been swapped at the same time.

On the macroscopic scale, things can have identity, because they aren't indistinguishable. They have different particles in different configurations following different patterns.

Identity is one of those things that makes sense in our experience, but which breaks down in extreme thought experiments because it has no fundamental truth to it and our flawed conceptions were only meant to work with what we have experience with.

1 comment:

  1. Apart from the inaccurate chemistry...
    The conclusion that: identity breaks down because it's a false perception
    is unfounded by your argument.
    Perceptions are deceptive because they cannot always determine everything that has or will happened. However they are not entirely false.
    Identity, I would argue, is a permanent state independent of the particles.

    Take a glacier that melts and flows into a stream and becomes part of the ocean.
    All of the states makes up a more complete identity of those particles. It's not that each state is falsely perceived, but that each state give more meaning and complexity to the identity of those particles.

    Logical arguments are flawed when they take Perceptions,place false conditions on them, and place them back into the world of perception to determine the accuracy of perception.

    Back to the initial philosophical puzzle of the boat. Two concepts are mixed here that make the puzzle confusing. 1) Identity given to something because of what it stands for, and 2) identity given to something for its physical properties

    example of how the two are incompatible
    1) America started with thirteen colonies and a very particular demographic. Now America is 50 states and compiled of a vast diversity of citizens. Are we therefore not the REAL America? Of course we are, because the identity "America" encompasses the whole state, not its parts.

    2) Mom made a hat. The hat was destroyed. Mom made a new hat. Was the hat the same. Of course not the raw materials were not from the same raw materials.

    Thus, the boat was not made of all original materials, but it was the same boat because it was given its identity by the crew. It doesn't seem to make sense on first glance that it could be the original boat and also not the original boat. In fact it is being classified by two different identities.