Yeah, that's good ****. Okay —
A) Can the destruction of "Fork B" be called "murder"? It seems that it is. If this person is not exterminated, it can continue existing in the world, if he is exterminated, the Cosmos is accounting for one less Consciousness in it. There's blood in the ground, there's a killer, there is an energy discharged to destroy this fork. I don't see how it is not murder;
B) Is the murder of "Fork B" dependent on the pre-knowledge of Fork B that he is going to die? That is, does the determination that what happens to him is murder depends on the words the scan operator tells you? If the scan operator is silently killing you, does that stop being murder? Clearly, that is ridiculous. People don't get out of jail sentences for being silently killing people.
C) Is the murder of "Fork B" dependent on the speed of his death? If he is immediately killed after the scan, can we say that the operator is therefore innocent of his actions? This is absurd: if he does not kill the Fork, the Fork lives as the laws of physics allows him to. It is the action by the operator that causes the extermination of the Fork. The speed to which he does this is irrelevant: He could wait an hour, he could wait a minute, he could wait a second, he could wait a micro-second. The murder is murder nevertheless, a Consciousness *has* been erradicated nevertheless.
D) Something has been hinted at the "suffering" of Fork B. Oh, the humanity, so concerned with the "suffering". It's a total strawman. You can easily depict a scenario where this person was given a drug before being scanned that prevented his psychological suffering. This administration of this drug does not absolve anyone from the crime of murdering him.
A) Sure, I guess you could call it murder, but I think that's because our concepts of 'death' and 'murder' aren't adapted to the realities of what we are — not single continuous entities with persistent existence, but a mind-state that changes every instant. I'd call this eradication of Fork B the same as day-to-day life (my favorite argument horse). Your mind state yesterday could've gone on living in any number of ways. But it was overwritten, it was lost, and only one way survived. What about the other ways it could have gone? They were lost.
I don't think you'll find this satisfactory: Fork B has
no causal descendants if vaporized after Fork A diverges. If you find that distasteful, it's pretty simple to ensure that Fork A only comes into existence after Fork B is gone. But to be honest, I simply don't think that the loss of a couple milliseconds (or even seconds) of existence is a major loss, or constitutes subjectivity death. I would use that 'roll your brain back ten seconds' machine with only a very little thrill of worry.
In my mind, our qualia and subjectivity
emerge from the physical brain. Consciousness
follows mechanism. If we wind the mechanism back, if we get drunk, if we take a head blow or get viral encephalitis, even if we get vaporized and then rebuilt from a couple seconds ago, we change. But we don't die.
B and C) This is a good question, and really interesting. I think it probes at the inadequacies of current ethics. If we do not tell the scan target he's about to be scanned and duplicated, no distress will occur, even if we wait ten seconds to vaporize one fork. The pre-scan individual has survived. One of the post-scan forks has died. I'll get into whether this is murder after I handle speed.
As for speed: it's all a matter of what you think about divergence. I'm
not worried about the fact that the fork could continue to exist, because your mind state yesterday might have continued to exist in any number of ways but it only got one. But I am, like you, uncomfortable with the idea of letting a fork diverge and then killing it.
Here is my cold-blooded fork answer: the person who steps into the teleporter can be absolutely assured that they will live. If one fork persists for long enough between the scan and the vaporization to experience subjectivity, then any divergence they undergo will be irretrievably lost. I'd probably be okay with this, but I think many wouldn't, and for that reason I think the teleporter should be built to avoid it. How long is too long? I don't know. You'd argue that any time is too long. You might be right.
D) Why not be concerned with suffering? If I am tranquilized and rendered unconscious before I go into the teleporter, I'm honestly...pretty okay with that, even if one of my surviving forks is vaporized hours later (as long as I don't wake up). All I'm scared of is the subjectivity of knowing that I'm about to die and leave no causal descendants.
Imagine that I fall asleep one night and develop an alternate personality in my dreams. I live a hundred years in dreamland. However, none of these experiences make it out of my short-term memory buffer, and when I wake up they have no causal effect on me. I never know I had this other life. From the post-dream fork's perspective, what was lost? Nothing. From the dream fork's perspective, what was lost? They lived, they died, but they never thought 'oh no, I am about to be murdered.'
What we are afraid of, all of us, is not the actual fact of stopping, failing to propagate our brainstate forward. Whatever. That's not inherently frightening. What we are afraid of is
creating forks who have to live with this knowledge, right? Or even creating forks who have experiences that will be lost, even if they don't know they're about to die. We don't want to be that person because
we will definitely be that person, even as we are also definitely going to be the other fork.
If I'm not conscious when I'm teleported/scanned/whatever, I can be sure there are no qualia getting lost. When my qualia reboot, they'll be rebooting from only my surviving fork. I'm cool with that.
Is that too freaky and posthuman to be sympathetic? I can understand how it'd be freaky and posthuman and disturbing. But I think it's an unintuitive but inevitable consequence of looking at this rigorously.