I have been thinking lately what I can contribute to this blog so that science doesn’t seem so utterly boring but rather gives you those brain teasers which end you up with sleepless nights. As I thought what the things were in science and scientific philosophy that attracted me most, I came up with only one answer: paradoxes and thought experiments.
From now on, I will be featuring some of the most famous paradoxes and thought experiments weekly. You guys are welcomed to share your views, opinions and own thoughts regarding the experiments!
One very interesting topic in philosophy is the concept of identity. Though it sounds quite redundant, but the question remains, what is identity? How do you “identify” something to be that particular object? A very famous and ancient thought experiment regarding the concept of identity is “The Ship of Theseus”. First brought up Plutarch around late 1stcentury, let’s see what Plutarch had to say, “”The ship wherein Theseus and the youth of Athens returned had thirty oars, and was preserved by the Athenians down even to the time of Demetrius Phalereus, for they took away the old planks as they decayed, putting in new and stronger timber in their place, insomuch that this ship became a standing example among the philosophers, for the logical question of things that grow; one side holding that the ship remained the same, and the other contending that it was not the same.”
—Plutarch, Theseus
Putting it simply, say there was a ship which had been sailing for 20 years needs repairing. As part by part as time goes by everything of the ship was changed. Say after 30 more years the ship had no pieces which was an original. Now the question comes, is this ship the same ship which you saw 50 years ago?
Most are inclined to say “yes”; after all you are just fixing the part of the ship but not changing it so it cannot be something different. This was same idea I had to face during my visit to the Great Wall. I thought the part I visited was built around 3000 years ago, the estimated timeline when the original Wall was built. But the guide told us that this section was destroyed due to earthquake and had recently been fixed by adding new rocks and stones. To them, it was still the “Great Wall” which was 3000 years old, not a piece of architecture which was mere 50 years old.
Or even consider the simple example of a river, say the Ganges. Surely the same water molecules don’t flow down the Ganges at every point of time, but we cannot assert or claim that the Ganges we saw yesterday isn’t Ganges anymore.
This idea develops from the fact that it doesn’t matter if the part of the object has been replaced, as long as it holds the “significance” and is able to give the “sense” of being the same old thing, we can consider it to be the original substance. As the Buddhist realists would say, “the Ship of Theseus remains so until it ceases to function as the Ship of Theseus”.
Now comes the real twist. Say someone was able to save all the parts discarded by the ship and after 50 years when all the parts were removed, he was somehow able to reconstruct a ship using the discarded parts. Now the question comes, is this the “original” ship or the one which you made by repairing? To put it mathematically, if your original ship was A, repaired ship is B and the reconstructed ship is C then either
A=B
Or A=C
But both cannot be true because if B=C then only one ship would exist, but you have two!
In this case, most people change their opinion and say “oh well, if it IS built by using all the old materials I guess C is the real A, not B”. But is it so?
I guess the main point which Plutarch tried finding out was when a certain identity loses its identity and becomes something else. Some philosophers did come up with some possible solutions:
- The Ship of Theseus is what it is by the individual parts that make it up.
In this case, the second you removed the first wooden plank from the Ship, it ceased to be. But the individual atoms in the wood are forever changing, with the result that the Ship is never itself.
- The Ship of Theseus is what it is because of its structure.
In this case, the Ship remains the same ship throughout the change so you have the seemingly inconsistent result that the Ship of Theseus is both B and C. Furthermore, when you have two ships (as in the last thought experiment), they both have identical structures, so you wind up with the result that both are THE Ship of Theseus – meaning that two discrete things are one numerical thing.
- The Ship of Theseus is what it is because of its history.
In this case, the Ship remains the same because of its particular role in the history of the world. Parts come and go, but the actor remains the same. You’ll still wind up with the problem in the case of Theseus duplicates, because each shares a relevant history with the “original” ship.
Let’s think of another possibility. We don’t repair any old part of the ship but simply take one plank out from the dock and switch it with a cabin plank. Is it still the same ship? Stupid question right? Well guess what, if you are somewhat scientific you should know about isomers where a simple rearrangement DOES give rise to a complete new identity.
Just to give you a question of thought before I end this, human cells are completely changed usually within a span of 10 years (estimated). So, if every cell in your body is changed after this span of time, are you really the person you were, when you were born?
Are you the person made of same matter? Breathe, and you’re no longer the same you.
Even though your cells change, you retain your original structure: Lose a limb, or cut your hair, and you’re no longer the same person.
You think you are a part of the history of “yourself”: Were you to be duplicated, you’d either have a existential twin, or you’d cease to be.
You had emotional change or memory loss: Lose your memories, and you’re no longer you. Have a radical change of heart, and the person you were once before is gone.
So, the question remains, who are you?
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