Ship of Theseus

The “Ship of Theseus”, also known as “Theseus' Paradox”, is a thought experiment that raises the fundamental question about perception of identity. Plutarch (Greek historian from 1st century A.D.) famously raised the question whether a ship that had been restored by replacing every single wooden part remains the same ship. *1

The first question about the ship of Theseus is, “In what moment or at what percentage during the change will the ship stop being the same ship and become something else?” *2

I will try to propose an alternative solution, very similar to what is already proposed in Solution 4 and 5 of the following video from Wireless Philosophy: *3

In an attempt to solve this puzzle, I will reach for a computer-based approach. First, imagine the simplest text document with ASCII letters inside of it. We will name that document ‘ship.txt.’

At the moment of creation, depending how we have done it, the document will have the date of creation, the name, and some kind of content inside.

By applying a hash function algorithm (md4, md5, sh-1, etc.) on the file, we will get the unique signature (fingerprint) of the document content (for simplification purposes, throughout the experiment we will imagine that signatures are unique). Any change of content will change the document’s signature, and thus it would not be the same document anymore. Similarly, physical objects are made of atoms and molecules; if we imagine that there is some machine that would be able to compute a hash algorithm on the molecular structure of an object or a living being, we would also get a unique signature.

During the hashing process, we exclude less important properties such as the document name and date of creation or updates. We can argue whether they have any intrinsic value to the document’s identity; similarly, we can ask the question whether changing of our forename, surname, or faking our birthday can have an impact on who we really are.

The document can be changed slightly during transmission. It can lose a letter or two (a ship and its parts can age). It can be scratched or damaged (a human being can grow, age, exchange nutrients or be injured). The trouble with a unique signature is that whenever one or more of these things happen, the signature will change as well. So, it seems that signature is not a valid approach to determine the identity of an entity (thing/object/being).

I will shortly digress. Ask yourself what it is that makes you, you? If I amputate your limb, will you still be you? Will you be you without that limb, or you will become someone else? If we replace part by part of your body, at what point do you stop being you? What if we were to replace your entire torso with an equally functional machine; would you still be the same person? Surely, you would have the same memories and personality regardless of the change.

What do you think is the most important part of you? Is it your head? Our memories and personality are mostly stored in our brain. But there are people who live without half of their brain. *4 Additionally, even without physically chopping our brains into smaller pieces, there are many things from the past that we cannot remember anymore.

Furthermore, many of our memories are distorted. We recollect many things differently than how they have actually happened. So, are we still the same individuals? Ultimately, what if I go so far as to replace every cell of your body with a compatible cell (cells that are a perfect match to the previous ones), at what moment will you stop being you?

Before jumping into mulling over the answer, you have to be aware that this is something that is already happening on a daily basis. Cell replacement is an ongoing process of your body; different tissues in the body replace cells at different rates, but that will not change who you really are, nor will you lose your identity. *5 Maybe this is because some cells (i.e. brains cell) never or very rarely change.
So, maybe identity is lost along with the part that actually carries the intrinsic value of an object or a being?

Moving back to our document example, we know from the “Shannon Theory” that a message can be read even if it loses a significant portion of its content. In addition, a document can be changed over time. For instance, books and stories probably never come into existence with one magic “poof.” Usually, they are made as a series of subsequent events, thoughts, keyboard strokes, spoken words, or pen writings.

With that being said, an important point of identity perception is time. Our perception of identity is a “state,” and that is misleading; of the many things that identity can be, it is more than often a “variable.” As philosopher Alan Watts *6 once said, we usually name things with nouns, but instead we should use continuous verbs. So instead of “nouning,” we should actually do “verbing.” *7 Hence, apple becomes “apple’ing,” people becomes “people’ing,’ document becomes “document’ing,” and ship becomes “ship’ing.”

Therefore, if we want to get to a state of one electronic document, we would need to take into account its creation, all of its changes, all of its copies, all of its branches and their copies, and everything else until that document stopped its “vibrating” life.

It is similar with books; they start as simple sketches, and slowly they turn into books. However, all those iterations, the ideas in the mind, and the copies and manuscripts represent the same individual book. Only after the changes stop and the book is written and corrected, we can fingerprint a book with the universal number ISBN. In a more global way, “book’ing” would represent the entire life of all the instances/copies of the same book object, with its lifetime in the memory of the world.

There you go, all the dimensional changes, all the time changes, and all the differences of all the copies and clones, all the toys, they all represent one same Ship of Theseus.

But, one more question arises. If two absolutely identical objects come into existence independently and serendipitously at the same time but in different parts of the world, and in the process they get different names, are they the same object or different ones?

I will leave that for you to ponder about...

Notes & References:

1. Ship of Theseus

2. The Paradox of Theseus's Ship (90 Second Philosophy)

3. PHILOSOPHY - Metaphysics: Ship of Theseus [HD] by Jennifer Wang (Wireless Philosophy)

4. Girl Living With Half Her Brain

5. Do We Replace Our Cells Every 7 or 10 years?

6. Alan Watts

7. Alan Watts - On Appling (and Peopling)