Actually, when you short a stock, you must pay an interest rate to the person from whom you borrowed the stock. That interest rate varies from stock to stock, but is always above the risk-free rate. Thus, if you short a stock and do nothing interesting with the cash and eventually cover it at the original price, you will lose money.

Isn't the obvious answer, "because, assuming your life isn't unbearably bad, living the next 1,000 years has higher expected utility than not living the next 1,000 years?"

We don't have accurate predictions about what the next 1,000 years are going to look like. Any probability calculation we make will be mostly influenced by our priors; in other words, an optimist would compute a good expected utility while a pessimist would reach the opposite result.

Responses like yours confuse me because they seem to confidently imply that the future will be incredibly boring or something.

I'm saying that if there's nothing impressive about my life in the present or the past, then I'm not one to expect much more out of the future. Some people have a cause or goal and would like to live long enough to see it through--good for them, I say.

I harbor no such vision myself. It's possible that something comes up at a later time and, over the course of 1,000 years (say), it seems rather likely that at some point I'd encounter that feeling. It's equally likely that something unavoidably bad comes up. On balance, I'm indifferent.

Honestly, I don't even find the prospect of living another decade all that exciting. If it's anything like its predecessor, my expectations are low. If I were to suddenly die in that time I wouldn't think it a big loss (albeit my family might not like it so much), but if I'm alive I'll probably manage to find some way to pass the time.

If you asked me whether I'd like to live another thousand years (assuming no physical or mental degradation), I'd ask myself "Why would I want to live 1,000 years?" and, failing to find an answer, decline. If I were told that I was going to live that long whether I liked it or not, I'd treat it more as a thing to be endured than as an exciting opportunity. The best I'd expect is to spend the time reasonably content.

Needless to say, I wouldn't make any great sacrifice today for that kind of longevity. If I avoid wanton hedonism, it's because that lifestyle can lead to accelerated degradation and the associated problems. Concern about longevity hardly enters into my calculations.

Significant lifespan extension would change all of our cultural norms so much that it isn't realistic to expect non-nerds to begin to wrap their heads around it in any meaningful way. And they sure as hell can't be expected to change their minds about any of their core beliefs/values, let alone the fact that they don't want to live "forever."

Yes, but Islamic societies don't actually have a Thought Police. They care about the public affectations and the obedience to norms associated with religion, not about private convictions. Honestly, do people in the West really think Arabs actually believe 100% of the nonsense they spout?

I support the idea of having a recurring 'Instrumental Rationality Questions' thread.