How do you define a person?

Yesterday night I was asking my friends to take the personality tests again and they produced different results than the ones they took last time, and many of them have borderline traits, such as between N and S, and J and P, or even F and T. This shows that it is not fair to fit personalities into pre-set models, because everyone is different. It also proves that people change.

We sort of know that we change with time. Yourself now compared with yourself two years ago is bound to be different. For example, I have looked through some of my earlier posts and realised how stupid they may sound, or how ideas are not fully or clearly explained. Maybe me now is still a bit different than me one minute ago. This makes the whole definition of me very fuzzy.

Have you heard of the Ship of Theseus paradox? In case you haven't, it goes like this.

Basically the question is: If you replaced every single plank of a ship, is it still the same ship?

Now, what if I tell you that every atom in your body is likely to be replaced and is different from the ones you are born with?

Are you still the same you? Of course, yes. You are still you. Even though the materials making up your body is no longer the same ones, this does not make you not you. Hence from this, I've came up with the thought that what defines something is not the materials themselves but more of a specific function, a very complex one maybe. Just like a mathematical function. With some input there will always be a specific output. Like your brain, like the specific way of how everything is structured, instead of the very atom making up the structure. 

Just like how three hydrogen atoms attached to a nitrogen atom is always ammonia, regardless of where the atoms come from. 

Therefore, even though all of the materials making the ship is replaced, the ship is still the Ship of Theseus. But if you take this approach, then as long as we take the same kind of material and build a ship the same way as how the Ship of Theseus is built, it will also be called the Ship of Theseus.

Just like if we analyse exactly how every cell in your body is structured and built one strictly base on you, the product will be also you. Who is you? Are there two yous, then?

In fact this thing do occur in nature, that's how you get twins. But why do we acknowledge twins as two individuals instead of one? Why are some twins so different in personality?

This comes back to the point I was making at the beginning. Because people change, and people change base on external influences. Yes, you may have two exact same copies of a person at the start, but over time their personalities will diverge, unless you subject them to exactly the same external influences which is impossible. 

That's the most wonderful thing about living beings. They receive external stimuli, then internalise them and make changes to themselves without realising most of the time. But this will also make identity difficult. Because we are constantly changing, we cannot take up a fixed identity. Therefore, it will no longer make sense if you are trying to define a person. The definition may be true for the moment, but it cannot hold true for eternity, and to us anything which can't last for very long will be dismissed as unimportant and useless.

So back to the paradox, identity will not make sense because there's change. Any change will destroy a pre-constructed identity. Because identity is forever. You cannot have an identity that is always changing. (But you can have many many identities that co-exist at the moments of change)

I've actually discussed this with some of my friends before. They were mindblown a while but they actually suggested very sensible solutions. YS said that whenever a new plank is added, the plank becomes part of the ship. Similarly, whenever a plank is removed, the plank will no longer be a part of the ship. This is entirely based on her intuition. I thought it makes sense but at that time I felt that something is not right. I was thinking "So what is the ship exactly?"

Some times I think that I think too much. The process of thought is enriching but I highly doubt the outcome of the thinking has much of value. Especially in philosophy. I can just live my life happily without all these disturbing thoughts. But I think the ability to think is something great, something unique to humans like a gift. We can choose to treasure and make use of it, or just live with the bliss of ignorance. I choose the former.