Noel: Ha ha! I made a perfect duplicate of myself!!

Rabid: That's impossible! You weren't BOTH at my birthday party, so you're not a perfect copy!!
Noel: Huh...

Noel: You're probably thinking I cloned myself and then copied my memories.

Noel: Then the clone would only REMEMBER the experience, falsely. And you'd be right.
Rabid: I guess?

Noel: But I made a special box that copied me atom by atom, perfectly!

Noel: The thing about atoms is that they are like cheques. If we trade a five dollar bill back and forth we can see if it was the "same" five dollars by checking the serial number on the bill.

Noel: Thanks!
Rabid: Thanks!

Noel: But a cheque just carries a magnitude! You can't ask "is it the same money" any more.

Rabid: I'm going to need to see some photo ID...

Noel: Make it out to "BEAUTIFUL Noel"! Please.

Noel: Each different kind of atom is indistinguishable from any other atom of the same kind: there are no little serial numbers on them.

Noel: It was a particular arrangement of atoms that attended your party, and that arrangement transformed over time into another arrangement. It was that later arrangement that was duplicated, and as a result, the copy has as much legitimacy to claim attendance at the party as the original! It's as perfect a copy as can be!!
Noel: Not any more! I got a hat!!