Life, Meaning and Time Discounting

Would life have meaning if we were immortal?

Or would we go through life as if nothing mattered because we have an infinite amount of it left anyway? So death is actually good, since it gives life meaning and purpose?

Conveniently to proponents of this line of thought, we currently do not have the opportunity for experimental validation.

However, where experimental validation fails us, we still have our impressively powerful minds to help us. After all, we can do math. Math is magic.

Present value vs. future value

As it happens, humans generally do not value all moments in time equally. Specifically, we care a lot more about things that are happening right now ("I'm eating this juicy burger, it's really good") or are going to happen in the near future ("if I spend $60k on this fancy truck, it'll be really cool to drive"). Less attention is given to the future, near ("... I'm not even hungry & I'll be really full if I keep eating") or far ("if I put the $60k into an index fund, the truck I can buy in 2050 for $200k would be amazing").

This does add up, especially over longer time horizons. As for investments, at a 5% rate of return, you could obtain 1000x-ish gains in just 148 years. While the personal value of time doesn't necessarily follow financials, it is a reasonable proxy still; after all, money is a metric of what humans are willing to exchange actual things for, at different points in time.

Of course, the model simplifies the world somewhat. After all, waiting 150 years until finally deciding to buy that truck is somewhat impractical, for multiple reasons. This doesn't change the point though: there is a general ratio of enjoyment of the present being preferred to enjoyment of the future, even all else held equal.

Of course, whenever there is a roughly stable ratio, you get exponentials. And, speaking of math, exponentials have the neat property of summing up to a finite amount, even if there is infinitely many of them.

(This is pretty easy to see. Let's say you're planning on having half of the fun you'll ever have in the next 10 years, half of that in the 10 years after, half of that one in the following decade, and so on. 50%, 25%, 12.5%... this all sums up to a hundred, while keeping a stable ratio of 0.5. The fact that the sum is finite does not change, even if you make the ratio less drastic; the only change happens when it reaches 1.0. That is, if you care about the present less than about any other point in your life, this does not apply to you. Fortunately, not very many people do this.)

As such...

The future contains a finite amount of fun

... subjectively.

Assuming, for now, that we stay reasonably human-like, and our current life mostly resembles the life that's coming in the following decades. People who don't want to be immortal generally agree with this, despite not being especially likely at this point... also, we are doing math and it's a neat model.

This means that the next day you will live through will contain a significant fraction of all the fun you will ever have, given your current point of view.

This makes it really truly important. You will have to definitely make it sure that it's a good day, otherwise you lose out on a significant part of the future you care about.

You can even calculate how much of the total niceness this represents. You will likely get a larger part, compared to people who derive this from their expected lifetimes! (Exponentials are powerful.)

Note, however, that our derivation does not require dying at any point. Once we are done with this day, we can repeat the exercise tomorrow, at which point the current day will yet again contain a significantly important part of the future, viewed subjectively. There is meaning. There is importance.

Past vs. future

There are important differences between the discounting of time in terms of fun vs. in terms of investments though. They might be similar looking forward, but they are definitely different looking backwards.

After all, you might feel that it would have been nice to have bought some Nvidia shares 10 years ago. Or having studied and learned a little bit more consistently, snowballing you into someone extremely formidable in your field. These are investments. It is useful to make them earlier. (Especially if they are good ones.)

But would you turn two weeks of your life into hell, just in order to be able to relive a nondescript Tuesday eight years ago, just for the fun of it?

(Not as an eager time traveler, filled with nostalgia, overjoyed with being able to relive a day of the distant past, fixing all the mistakes... but as the boring Tuesday it actually was, living through the same moods.)

That particular nondescript past Tuesday is not much more important than today is. Actually, today is a lot more important and fun, no matter whether we compared to that Tuesday or the nondescript Wednesday years into the future.

All this leaves us in a pretty good spot. As it happens, there is no need to be depressed about past days we thought were important, because they are not that important anymore. (Remember the last time something hurt so bad you took painkillers? Would you prefer swapping it with the present, so that today is a memory & that day is actively happening?) Meanwhile, there is no infinite boring desert of rows and rows of future days staring at us menacingly: there is just today, tomorrow... and there is the rest.

And then once we are done with tomorrow, we just seamlessly rescale everything; we can look forward to a similarly front-loaded amount of fun and importance the next day.

Even if we lack a mandatory endpoint.