Two Philosophical Bits

Are you the same person you were last week? How long should you shop?

Big Think, Philip Perry, 19 Oct 22 (seen today via Fb): This ancient Greek thought experiment will have you questioning your identity, subtitled “How much can something change and still be the same thing?”

This is a familiar philosophical conundrum, which goes back to the notion of owning a ship, like the one in the illustration above, and over many years gradually replacing all its parts. If eventually you replace all its parts, is it the same ship?

My preliminary thought (preceding this particular issue) is that ancient philosophy is mostly based on presumptions (guesses) about the world that have turned out to be false. (Another comment I recall is that philosophy is a history of failed models of the mind.) Philosophy still has good questions to ask (about which kinds of things are more important than other things, e.g.), but throughout history most of its speculations have given way to scientific discoveries about what reality is actually like.

And thus my first thought about this article is this: that all the atoms and cells in your body are regularly replaced, even brain cells, over days, weeks, or months; it’s the assembly, not the individual components, that constitute your essential being. So your identity is not hinged on your parts, anymore than the meaning of a book is hinged on whatever pages, in whatever typeface, it’s printed on.

The writer here has anticipated this, opening with:

It is a myth that you get a new body about every seven years. After all, different cells last different lengths of time: Colon cells last only about four days, skin cells two to three weeks, and neurons last a lifetime, not to mention that your tooth enamel never regenerates. So even though the body you are in now isn’t quite the same as it was last week, last month, or last year, it is not completely different as it was when you were born.

Still, the myth raises an interesting question: If you were to incrementally remove parts of an object and replace them with new parts, at what point would you say that object has become an entirely different object?

This site, Big Think, presents think pieces like this regularly. They are not about currently contentious issues, but they are about issues worth thinking about, especially for people who’ve never thought about such things before.

My take: of course it’s the same ship, and your same body; both have an existence that is independent of, and is emergent from, any individual components, however much those components might keep changing out.

To its credit, the article goes on to allude to my second thought about this notion (that I had before reading it). Given that the Earth is turning, that it’s orbiting the Sun, that the Sun is orbiting the center of the Milky Way galaxy, and so the entire solar system is moving through space in a combination of various vectors… what does it means to return to a particular place on Earth, say your hometown, and think that it’s really the same place? It may be the same *relative* place, to the rest of planet Earth, but if there is kind of anchorage to the universe of fundamental places, then it can’t be the same place. You can never return to the same place twice; it’s not the same place. (The answer to this is, of course, that there is no fundamental stability of time and place; everything is moving, everything is relative. This has been a headache for various science-fictional speculations about teleportation, whether from orbit to surface, or across interstellar distances; and for time travel, which tries (or not) to take into account the moving position of the Earth across the ages.)

The article doesn’t quite get this, but does say this:

One common answer is known as spatiotemporal continuity.

This says that all objects change continuously as they travel through spacetime. As such, they’ll have parts replaced from time to time, or may even change form or composition. Yet their identity remains. The famous Greek philosopher Heraclitus posited that we don’t step in the same river twice. Everything is constantly changing, though we’re not likely to notice.


On a similar site is this (again seen on Fb though posted a while back).

Freethink, Jonny Thomson, 17 Aug 2022: Mathematicians suggest the “37% rule” for life’s biggest decisions, subtitled “How many options should you try before you commit? This is known as the optimal stopping problem.”

I’ve heard about this before, and it addresses the idea of how long you should keep shopping before finding a product you can settle on. I’ve known people who will shop endlessly, comparing all possible products to find the perfect one, no matter how much time it takes; compared to people like me, who will search to find an adequate product, then buy it and go home. My partner likes to shop more than I do, though he’s not an obsessive perfectionist. What I keep advising him, when in a quandary about which option to buy (this turquoise color or this more greenish color?) is to say, once you get it home, you won’t remember these options, and you won’t care. Just get something that’s good enough.

The article opens:

It’s time for Macy to move home. She’s scored a promotion and she’s tired of hearing the man in the apartment above play his French horn. So, she books a few viewings with her real estate agent and starts looking at houses. After looking at three places, she falls in love: It’s a house with a huge backyard and a nice open-plan kitchen. What’s more, the school down the road has a great reputation. She’s all set to put in an offer.

But that night a question pops into her head: What if the next house is better? She can’t shake the thought. What if the next house has a bigger backyard, or maybe a double garage? What if it’s cheaper?!

Cut to the chase:

The mathematical question for Macy (or our would-be dater looking for love) concerns maximizing probabilities. It’s asking how long do you spend sampling options to give the optimum chances of a successful final decision? How many frogs must you kiss to secure your chances of getting a prince?

Mathematicians have given us an answer: 37%. The basic idea is that, if you need to make a decision from 100 different options, you should sample and discard (or hold off on) the first 37. The 37% rule is not some mindless, automatic thing. It’s a calibration period during which you identify what works and what does not. From the rejected 37%, we choose the best and keep that information in our heads moving forward. If any subsequent options beat that benchmark standard, then you should stick with that option to get the best ultimate outcome.

Of course humans are not rational.

Mathematics offers us the best answer to the “optimal stopping problem.” But there’s just one big issue with it: Humans are not rational probability-crunching machines. In fact, the opposite is usually true. We’re beautifully, infuriatingly, creatively, and messily chaotic. So, it falls on psychology to tell us about how we actually behave.

The article goes on about the “explore/exploit” tradeoff, which ties in with how curious or risk-seeking we are. (Here we tie back to those ranges of human moral foundations!)

The article concludes:

As a general rule, though, 37% is a good one. When it comes to buying things or making life decisions, it’s a mathematically safe starting point. There’s a lot of wisdom to be had in sampling the field before settling down. It’s about doing research and calibrating expectations. It’s all about learning what makes something good or bad, and just what you want in a thing.

When will you use it first?

And this piece was first published at Big Think too.

This entry was posted in Philosophy, science fiction. Bookmark the permalink.

Leave a Reply

Your email address will not be published.