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Comment by chongli | Hacker News Reader

You know you're the same person as yesterday because without you, there is no knowing. A clone is no more you than an identical twin is you. What makes you you is the ability to ask the question in the first place. If you were dead, there would be no question.

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I don't follow.

You know based on your ability to ask the question that you currently are you and not a clone of yourself, but you don't know that the person yesterday was you and not some other person that you were cloned from.

but you don't know that the person yesterday was you and not some other person that you were cloned from.

The parent did not say anything about this and neither did I. Of course you cannot know whether you are a clone or not. My point is that if a clone is made of you and you are killed, you will be dead, you won't be the clone.

You both did.

> When you wake up the next day, how do you know you're the same person as yesterday?

> You know you're the same person as yesterday

Why is there no knowing without a you? Won't the clone know just as well as you that he's you?

What defines "you"? The matter you're made of?

Is it a particular arrangement of that matter? (Would you care if your neurons were replaced one by one, while keeping the same arrangement?)

Is it your memories, your thoughts, your inclinations?

Or is it something else?

Because when I die (or anybody else dies), the universe ends for me (or them). The clone is just a different person who can't tell that he's not me. But he is him.

The only thing you can really know for sure is that you're still alive. When you're dead, you know longer have the ability to know.

I guess my question is, yes, you can know that you're still alive, but how can you know that you're still _you_?

What a weird question. You're always you, until you die. Even if you became totally paralyzed, blind, deaf, etc. (total sensory deprivation) you'd still be you. All that is you is just the voice in your head, the ability to ask the question, and to think about an answer.

As for what happens to your body or anything else in the world? You can't ever get rid of those doubts. The only thing you can know without a doubt is that a doubter exists. Cogito ergo sum, as Descartes wrote.

In context of the thought experiment there can be more than one person with equal claim to be the person that you believe yourself to be. For example, given the postulated copying technology there could be Two or ten or a hundred people with the same claim 91 you to be today's version of who you remember yourself to be. The only thing that makes one person's claim better than another's is a perceived continuity of physical substrate. But even that perceived continuity is at least partly a fiction, since the physical substrate isn't really the Same from one day to the next, or even from one moment to the next. Bits of it are always being swapped out, lost and replaced. It's a valid question to ask, in that context how do you know when you wake up that you're the same person who went to sleep? Why do you think you are the same person, as opposed to an entirely new person who happens to have inherited a particular batch of ingredients of memory for assembling a story about who you are?

My argument is that you don't really know other people, you only know yourself. Clones don't even have to be physical replicas of people, they need only be entities or systems which can pass the Turing test. The fact that a clone may think it is me makes zero difference to my friends who have no way of knowing and it makes zero difference to me because I can clearly see that it is a separate person from me.

Now, you could contrive a thought experiment where you clone me in such a way that neither I nor the clone know which one of us is the clone, but then, how is that any different in principle from babies switched at birth in a hospital?

Your memories don't define you, since they may be false. The only thing that defines you is your consciousness in the present. Everything else is I/O, and subject to interpretation and trust.

My point is that you don"t know yourself, either. You know in any given moment whatever self you have constructed from the sensations, emotions, inferences, and memories available to you. It "s conventional to assume that there is continuity with the selves that you remember, and that"s the default common sense position to take--a sort of pragmatic shorthand--but we don"t actually know that the continuity is real.

In fact, we do know that human memory is spectacularly unreliable, and, moreover, that it is a virtuoso liar, very accomplished at convincing us that we vividly remember things that never actually happened. It's proficient at rearranging memories and sensory impressions into ad hoc stories that we uncritically accept as true records of events.

From this point of view it seems a little over optimistic to me to say that we know ourselves, or to say that I know that the me of today is "the same person" (whatever I might mean by that) as the me of yesterday or last week or 1965.

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