Many arguments have been deployed in support of greater investment in the development of rejuvenation therapies capable of treating aging as a medical condition, and ultimately bringing an end to age-related disease and mortality. Personally, I'm in favor of rationales based on individual freedom, as "we can try and we want to try" is entirely sufficient, and utilitarian concerns based on reducing the amount of suffering and death in the world. Since aging is by far the greatest cause of human suffering and death, and since the estimated cost of developing working rejuvenation therapies based on the SENS vision is compares very favorably what is spent every year on trying and failing to cope with the harms caused by aging, it only makes sense to forge ahead. Would that everyone saw things so clearly, but of course we don't live in that world yet. Advocacy for rejuvenation research and medicine to control aging is still very much needed, as most people simply don't care, and many are even opposed to this grand project when it is first presented to them.
Biogerontologist Aubrey de Grey, the father of SENS, a plan for the development of rejuvenation therapies based on repair of cell and tissue damage, always likes to answer to all objections and concerns regarding rejuvenation with two general arguments. The core of the first argument can be expressed quite succinctly: are any of the potential problems that might be caused by rejuvenation in the future worse than the actual problem of ageing we have today? By and large, the yardstick by which we measure a problem's magnitude is typically the amount of suffering, misery, and death it inflicts on people. For example, when war breaks out we do regret the destruction of landmarks and infrastructure, but that's hardly how we measure how bad the war was - rather, we speak of how many lives it has claimed or how many people it has maimed. Around 100,000 people die every day of ageing - that is, of the pathologies of old age and their complications. This is a huge number, and it is a whopping 2/3 of the deaths that occur every day (around 150,000). In a year, that adds up to around 36,500,000 deaths. According to the most conservative estimates, around 50,000,000 people died in World War II (1939-1945); on average, that is about 8,400,000 people a year. Thus, in a year, ageing kills about four times as many people as WWII did in the same timespan.
By this measure, the problem of ageing is really bad, killing every day more people than all the other causes of death put together, and causing enormous suffering as well. If we successfully implemented a comprehensive rejuvenation platform, the problem of ageing, and all the misery it causes, would disappear altogether. Do we think that the potential side effects of defeating ageing may be so bad that we would be better off not doing it at all? For each problem that you think the defeat of ageing might cause, you can ask yourself if it would be worse than the problem we have today - the misery, suffering, and death caused by ageing, not to mention the socio-economical problems it causes as well.
The second argument is that we should not presume to know better than the people of the future. There are many objections concerning potential future problems. However, the truth is we know very little about the future, especially compared to what will be known by the people who live in that future. It would be arrogant to assume that a problem today will necessarily be a problem in the future as well. Just imagine if our forefathers two hundred years ago had reasoned: "Vaccines could cause the population to spiral out of control! They would save a lot of lives, but those very lives would go on increasing our numbers, in a way or another, and in a couple of centuries billions of people would be walking the Earth! How could we possibly feed so many mouths? Better to forget about vaccines and let nature take its course. It's a necessary evil."
Today, we are in the same situation as our ancestors in the example above. If we say 'no' to creating rejuvenation today, we would be condemning not only ourselves, but the people of the future as well, to the diseases of ageing; worse still, we would be doing so on the questionable assumption that we know enough about the world of the future to decide rejuvenation would do it more bad than good. If we develop rejuvenation, we will give our descendants (and possibly ourselves) the option to use it; if we don't, we will deny them this option and force them to suffer from aging. One day, our descendants may either be thankful that we gave them a choice between health and disease, or regret that their arrogant and unimaginative forefathers didn't think the matter through before deciding on behalf of humanity of the future.