Derek Parfit, 1984
It scans you here and builds you there. Is the one who steps out you?
You step in, every atom of you is read, and an exact copy is assembled on Mars. The original is destroyed in the scan.
The one on Mars has all your memories, your family, your debts. From the inside it felt like a blink.
Is that you? Or did you just die, and a very similar stranger begin?
Parfit then closes the exits.
Suppose the machine glitches and the original is not destroyed. There is a you on Mars and a you on Earth. The Earth one is told the scan was harmful and they have days to live.
If the Mars one really is you, there is nothing to worry about. You live on.
If that is no comfort, you do not actually believe that continuous memory makes the same person. So what does? This is where most people run out of answer.
His conclusion is unusual: the question "is it the same person" does not matter much.
What matters is how much connection there is — memory, character, intention — and whether it comes bundled as one person is a label added afterwards.
Parfit wrote that seeing it this way made death less frightening. Your self twenty years out already differs from you in memory and character. Connection is always thicker or thinner, and there is no line.
Every night
Consciousness stops overnight. Is the person who wakes the person who slept? The only difference from the teleporter is that the body continued.
Lean on the body and you are back in the Ship of Theseus.
Migrating your data
Move everything to the new device and wipe the old one. Same contents, same setup — nobody objects.
The objection appears only when it is a person, which means something beyond the contents is being counted.
You, twenty years ago
Cells, memories and tastes have largely turned over. Still the same person, officially.
By thickness of connection, the copy on Mars and your twenty-years-ago self are not far apart.
If you take one thing
If it were cheap and ten times faster, most people would step in. Philosophy tends to go quiet in front of convenience.
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