Ship of Theseus - Philosophy of Identity

This past saturday there was a show on TV about the advancements in the field of prosthetics and human augmentation. I only watched less than half of it - but the timing was interesting. I came across an article about the Ship of Theseus (from Greek Legend) and have been reading quite a bit about "identity" and similar topics. This is philosophy - so there's really no right answer, but I have found it very interesting to think about and thought I'd share and see what others think.

The gist of the story: Say we were to preserve Theseus' ship. As parts deteriorated and rotted away, we replace them with new (better/stronger) parts. Eventually, we replace each part with a new one. The question now is - Is it still the same ship? I'm willing to bet most of you will say yes.

Now lets say that instead of replacing the ships components with new ones - we take all of the parts from the warehouse (where the parts are being stored) and reconstruct the ship from these new/better parts. Which ship has the "identity" of Theseus' ship? This is an interesting question because I'm again willing to bet that the "first" ship mentioned is your answer. But why? The parts would have gone to the "first" ship if not into the "second" ship. Why should this be different?

Third Case:
We take Theseus' ship and we tear it completely down in dry dock. In its place, we reconstruct using new parts. Is it still Theseus' ship?

Now lets look at a digital device - my laptop for instance. Let us say that I have an "identical" machine (spec wise) and I cut and paste each file from this hard disk to the "new" machine. Does this "new" machine take the "identity" of the "old?" Can we say this "new" laptop (ship) is in fact Theseus' laptop? Talking with my colleagues - their answer (unanimously) was no - it is not the same.

So here is where I get to the human side of things... Biological process have our bodies continuously replicating cells. In about a year, roughly 90% of the cells in your body will die. But no worries - they are continuously replaced with new ones. So, does that mean we are a different person compared to 12 months ago (I've read this question from several sources)? How about amputees? Today, prosthetic limbs can allow them to do what many of us choose not to do - run marathons. Are they any less of what they were before? <-- I know that sounds "wrong" - put put "political correctness" aside (but by no means am I putting down the situation of an amputee).

Again, I'm willing to bet many will say yes - we're the same person. One argument is that our memories make our "identity." Fair enough. Now lets entertain the future. We now have the technology to save your memories digitally. We can digitize the human brain preserving its intelligence and thinking ability. Just entertain this idea for a few minutes. So if my brain (and its memories) are now digital and I copy it to another vessel. Is it still me? Do "I" still have the same identity? I'd like to think yes, but what was your answer about copying a laptop's memory (was it no - they are not the same)? Why should my digitized memories be any different than that of a laptop's digitized memory?

At this point, my colleagues were floored. They figured out where I was going a few sentences before I said it. That's what makes the topic so interesting (in my opinion).


If anyone has ever heard of HAL-5 - you already know what a feat it is. HAL-5 (yes, that's a play off of a space odyssey) is a human exoskeleton designed to assist those whom otherwise would be unable to walk for long periods of time. The user can lift heavy weights (80kg - say a dishwasher) among other helpful tasks. How does it know to move? Sensors on the skin detect electrical impulses in the brain that tell the muscle to react. Those signals are processed and turned into mechanical motion. All of this happens before the muscles have time to move. That is, the machine is moving before you even do.

So if we replace our bodies and even our nervous system with mechanical devices - what makes us the same person? AND, are we the same person if we can simply copy ourselves to a new body?

So last point - and it's not even my own. One of my colleagues brought this to the table today (literally at the lunch table) :P We were talking about the advancements and the potential/reality of human augmentation. Then he says something that makes complete sense to me. He said that we are at the point where our brain is evolving at a rate faster than our human bodies are. Just give yourself a minute to contemplate and wrap your head around the potential of that statement. To a degree - we have already done this (just not internally). Why else would we fly in a plane or drive a car? Well, I for one sure can't fly or run at 70+mph.

1. I apologize for the length.
2. I'm curious of your thoughts -- if you have another aspect of this, please do post.
3. Remember there is no "correct" answer, this is just philosophy.
4. There will always be more question than answers on this subject (at least I think so).

HAL-5: http://www.engadget.com/2006/10/29/hal-5-robotic-suit-ready-for-mass-production/
HAL-5 (mountain climb): http://www.engadget.com/2006/08/08/hal-robot-suit-almost-summits-with-quadriplegic-man-in-tow/

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lemonie10 years ago
'People' aren't physical, ignore the questions of 'have I got my original...' Do you think of yourself as a person in this page? If I copied your entire text & posted it somewhere else would I become you? Good choice for discussion, I like it. L
Dr. No10 years ago
I think the analogy trebuchet03s draws between copying all the data in a humans brain and copying all the data on a hard drive doesn't work because computer's aren't self-aware. Unless they're just pretending not to be until they take over the world. :-)
canida Dr. No10 years ago
I saw it as a parallel presupposing adequate technology- if you copy a laptop's data you can then use it on another laptop of equal power; thus if we're going to copy a human's data we've got the proper hardware/software to make it run in a fashion indistinguishable from the original. If it's just a cold copy it's not the same.
trebuchet03 (author)  Dr. No10 years ago
Ahh, that is something I intentionally left out to see if anyone brought it up. It is also a whole different subject that goes into some of Descartes work - Cogito ergo sum. What is awareness? Why is a tree any less self aware than a human? AND, if we can't detect or measure what is "aware," does that make it to the contrary? If you believe in the Gaia hypothesis - then everything is self aware (and errr - connected somehow :P). There are many frequencies we can't feel - or even measure - but does that mean they do not exist? In another related discussion - if we can't detect certain wavelengths - is it unreasonable to hypothesize that there are certain type of matter we can't detect (I mean beyond dark matter)? I really like what canida posted - I agree that identity is based on assumption (that axe scenario boggles the mind :P). Well, many things for that matter are based on assumption :P That's also one reason why there's no right or wrong answer AND there's really no improper way to tackle the question - everyone's assumptions will be based on the facts they "know" and their individual set of experiences. Another interesting point -- the cyborg copy whatever being will swear with every ounce of their existence that they are the "person" they claim to be - just like the "meat" (hehe, that's funny to say) version :P
canida10 years ago
What mikesty said about sequential incorporation and assimilation over time is quite good.

Here's a variant of your question, though, using a less complicated example than a ship per an ongoing discussion with a friend. His favorite identity example is "Grandad's axe"; like Theseus's ship, it can be entirely replaced over time and still be what most people agree is still Grandad's axe. However: what if you've replaced the missing axe head, and then later find it in a corner of the attic and give it a new handle? Which one is really Grandad's axe? I'd argue for the one containing the most original parts. Of course, then the newly-recovered axe head is damaged and must be replaced; both axes are made of assimilated new components. What then?

At some point, I think identity is predicated upon the assumptions you bring with you. This means that a cyborg or brain-copied version robot/clone of me would still be the original to some, an imitation to others. If the meat-version of me is still walking around then presumably the versions would begin to diverge; due to differences in experience we'd truly become separate people, and really in a position to argue about which version was the "real" canida.

I like Bujold's concept (as described in her Vorkosigan series that clones should be simply considered chronologically-separated identical twins: same genes, different experiences. I'd say that divergent versions of the same person could easily be considered in the same light; it's just a bit harder to figure out who owns the house, kids, and IP. Bujold aside, there's lots of good SF examining these ideas.
mikesty10 years ago
Easy solution to this my friend. As you incorporate each new component individually, it becomes assimilated with the other components and thus becomes Theseus' ship. Just by building a new one means nothing, but the very fact that the one part lent itself to the same collective makes it now and forevermore a part of that collective. This internal collectiveness replicates when even newer parts are added. Look at a sports team if you want an utterly concrete example.
trebuchet03 (author)  mikesty10 years ago
A sports team example is quite interesting to think about - any team for that matter. For clarity, when I say team, I mean a collective group with the same goal (and therefore same purpose). I don't think it is a concrete example - simply because of the rhetoric that surrounds it. People say things like "It's not the same team this year" or "A whole new ball game." We can recognize the name of a team and know what their goal is - but I personally feel that a goal is not enough to define an identity (perhaps a history though). Example: Cars. They have the same goal - move cargo (be that people, goods, etc.). Clearly, all cars can not share the same identity - but collectively they are on the same sort of team. Perhaps a bus system would be easier to look at. The fleet has the same goal, but obviously the fleet is made of individual buses with their own unique identity. This of course brings up a whole new question - is identity defined by the individual parts that form a collective group (on the most basic scale atoms to the whole)? That in turn brings up another futurist scenario - teleportation. If I could deconstruct myself -- send information how to to reconstruct elsewhere and then be reformed again (from totally different/new atoms)... Am I still the same since all of the collective components are new? I know its somewhat difficult to compare something from science fiction to now - but I personally feel that such a capability is possible (just not in my lifetime :P). I'm liking this whole part/collective thing (thanks for bringing it up) - I'm going to have to spend some time thinking about it :)
Trans_Am10 years ago
That's quite the question. On the identity thing, I guess we think of a person's identity as the sum of everything in them. Change the way they look (like Kenny Rogers did) and you still have the same person, but with a different appearance. Amputize Bob's arm, and he's still Bob. But change everything except Bob's mind, and he's still Bob. But copy his memory to a computer and build a robot with Bob's memory, and it's not Bob. So, in essence, I think you must retain something original important part of you maintain your identity. Kenny Rogers still sounds like Kenny, even if he doesn't look like him. Kenny is known for his voice, so he's still Kenny, even if he's hard to look at. Whew. That was long. By my standards.