It seems to me that if you're a materialist, then Cryonics is a pretty good bet.
When you die, you get your ass frozen in liquid nitrogen.
The argument that convinces most programmers that this might work is: 'this is not a secure delete algorithm'. If you take the hard drive out of a computer and put it in a fridge, then later on, you can read the data off it even if the mechanism's buggered.
If you want to make sure the data is not recovered, then you have to work a bit harder. If you put it on a bonfire for example, then that data is never coming back.
All the traditional methods of corpse disposal are bonfire-like. No way to reconstruct the information that was once there.
But cryonics will preserve the brain in the state it was a few hours after your heart stops, and at that point, we can imagine (with some difficulty) reading out the connections between the neurons. If that's all there is to being you (which is our best guess), then we can either (with difficulty) rebuild a brain with that wiring, or (easily) run a computer simulation of one.
And any good materialist has to reason: "I can have a conversation with this new person/computer program, and he will claim both to be conscious, and to be John, and be quite sincere in that, so I had better accept that he is John."
But of course, once we've done this, do we destroy the original body? Do we destroy the records?
What if, one day, long after your new self has headed off swanning around the Milky Way, someone finds a way to resurrect the actual body, rather than just the pattern? Which of these two people is you? What if they just make two copies of you? What if they slow down the clock on the computer simulation so much that the next scheduled tick is after the heat death of the universe? Have you just died again? Should you mind?
It looks like we're about to build a transporter. In our real universe, not our fictional one. Which of course is why I'm currently worrying about the morality of Star Trek. It's easier to think about, but the issues are the same.
It gets worse.
If you throw your hands up and decide that the future cop(y/ies) of you aren't you in any sense that matters to you (no one else will notice any problem), then consider the following:
When you go to sleep, you lose consciousness. Overnight, the configuration of your brain, the very atoms of your brain change much more than they would in an hundred years of cryonic storage.
If the cryonic you isn't you, then neither is the you that will be tomorrow.
Do you believe that you die every night, and someone else wakes up every morning?
If that's true, it's not so bad. We've been putting up with it for ages, and never suffered the slightest inconvenience by it.
If you give someone a drug that makes them sleep for days, have you killed them?
If you give them a drug that makes them sleep for years, have you killed them?
If you freeze them while they are asleep and wake them up thousands of years later, have you killed them?
If you freeze them while they are asleep, keep them revivable but never revive them, at what point did you kill them?
What the hell does it even mean, to be immortal?
Consciousness, we directly experience. No philosophy that does not account for it is acceptable to me.
Continuity of consciousness, not so much. Why should I care whether or not someone who isn't quite me, but who is quite like me, rises from the dead in 100 years time?
But then if I buy that and decide I don't care, why should I care if someone who isn't me, but who is quite a bit less like me that the revived cryonics patient would be, rises from my bed tomorrow morning?
So can anyone come up with an argument against cryonics (which costs around £30000 plus hassle) that doesn't also imply that if I thought someone was trying to kill me in my sleep I shouldn't mind?