The world has become prosperous. Population has stabilized at 10 billion. All is well in every way. And now scientists are working on a cure for aging, a pill that will increase average life span from 75 to 150. If people live longer, they will have to produce half as many children (to avoid a drain on resources). But this helps a bit: the pill will have a secondary effect of making fertility last to age 50. And we are to assume that the super-elderly would retain the abilities and vigor of people in their 60s and 70s.Singer and Blackford think the 150/1 life is better, so at first glance (they think) we should develop the drug. As I said yesterday, I find this dubious. The 150/1 life may include a lot of second-half dullness and less first-half joy and satisfaction--due to the reduction in child-bearing and the absence of siblings. To think the 150/1 life is better requires taking a "total view" of life assessment. You add up happiness enjoyed on day 1, day 2, to the end. More total happiness makes for a better life. But that doesn't mesh with how we normally assess our lives. We are not especially impressed with a dully pleasant super-long life, just because it yields a high total. Better to live a shorter life with higher highs--at least many of us think.
Should the anti-aging pill be pursued? There are a couple of crucial questions. (1) What's better, a 75/2 life or a 150/1 life? (2) What of the fact that there are half as many people in 150/1? Should halving the world's population concern us?
So I don't think the drug is attractive, even at first glance. But let's assume it is, just to see what the dispute between Singer and Blackford is all about. Halving the population creates a problem, according to Singer. That's not because we should grieve for the missing people. It's just because it affects the math. Here's how it works--
The good in a 75/2 life is, say 100. They assume that in the first half, the good in a 150/1 life is also 100, but in the second half it's just 90, because of age-related decline. So--a total of 190.
With 10 billion people living 75/2 lives, there are 1 trillion units of good. With 10 billion people living 150/1 lives, there would be close to 2 trillion units of good. So--fantastic! But of course you can't have that. Once everyone is taking the life-extension drug, the population will go down to 5 billion. There will be 5 billion times 190 units of good. That's under 1 trillion, less than the total good in the 75/2 world.
Singer thinks we ought to take those totals into account when we decide what we should do. So we should not pursue the life-extension drug. Blackford thinks the total view here is incorrect (though the total view of life assessment is correct). So there's the disagreement between them.
Why be against the total view here? There are lots and lots of super-tricky issues involved that bear on all sorts of questions in applied ethics. To be continued...