> On the other hand, you can accept that both of us (along with every human alive today) will die. [...]
Why should I accept this? Humanity hasn't been improved by accepting that it was natural for people to die of smallpox, or be crippled by polio. The belief that such diseases could be eradicated was the first step in doing so.
Our limited lifespan is just another thing for us to defeat as a species. I like to imagine some far-off future where parents tell their children about our mortality in the same manner that we are told about diseases like smallpox.
Because curing smallpox and polio are specific, well constrained goals, while curing death is open ended and not even well understood on a fundamental level. It's like saying that because you can earn a paycheck above poverty level, you can be richer than Bill Gates, Carlos Slim and King Midas put together. In theory yes, but this reasoning fails to address important practical concerns.
Regarding immortality, you have to remember that every time a major death cause has been neutralized, the probability distribution reorganizes itself and other death causes raise to pick up the slack, even causes which used to be unknown/negligible a few decades ago. That's to say, every life that has been "saved" from smallpox, polio or whatever was not really saved - strictly speaking those people still died (or will eventually die) anyways of a different cause.
That's not to say that life expectancy cannot be extended, or that that is not a worthy goal in itself. But there is still the practical issue that the clock is ticking for every one of us. According to current data, I am expected to live another 40 years or so. During that time, the line can maybe pushed another 10 years, and combined with positive lifestyle changes, having won the genetic lottery in the form of my family having a track record of many long lived members, and a bit of luck too, I don't think it is unreasonable to think that I personally might make it to 100 years in a relatively dignified state. However, that's it, I will already be old and wasted by then, and the only hope I can think on how to extend that even further would be Deux ex Machina.
Now consider the scenario for a baby born today. Maybe those 100 years will give him plenty of time for science to progress and fix a lot of things during his own time... assuming no major threats raise caused by our increasingly industrialized lifestyles, which is doubtful. Maybe all the things considered he will live to see a time when 150 is the average, and he may be able to push it to 170 by being smart and having a lifestyle healthier than average... but that's it.
If I were extremely optimistic, which I find hard to be these days, I would say this trend will stagnate around the 300's due to the law of diminishing returns. So, our descendants might see a time when dying at mere 100 years old is a tragedy, but there is a world of difference from that and actual elf-style immortality (never age or die but by an act of violence that destroys your physical anchoring to this world).
Why should I accept this? Humanity hasn't been improved by accepting that it was natural for people to die of smallpox, or be crippled by polio. The belief that such diseases could be eradicated was the first step in doing so.
Our limited lifespan is just another thing for us to defeat as a species. I like to imagine some far-off future where parents tell their children about our mortality in the same manner that we are told about diseases like smallpox.