A Longtermist Effective Altruist Argument That We Must Invest All of Our Money in Time Travel

The core ethical insight of longtermism, as championed by William MacAskill and picked up by many effective altruists, is that people have equal moral weight, no matter when they live. We are morally obligated to the next generation, the generation after that, and all the generations that follow. ‘Now’ is not special, and we are not morally privileged, just because we happen to currently be alive.

While I have for years believed, naively, that actually existing mattered to moral calculus, I have recently become a staunch believer in long-termism. People currently alive, the next generation of children who will certainly be born in the next few years, and all the trillions of purely hypothetical humans that may exist across all possible futures are all morally equivalent. I have shed the silly, humanistic deontology of my youth and am now a rabid believer in longtermist consequentialism.

Like all adult converts, I am rabid in my faith. In fact, my only objection with long-termism as it is currently practiced is that it doesn’t go far enough. It’s true that all possible future humans are equally morally worthy, but so are all past humans who lived before us and have already died.

You see, just as now isn’t special, neither is the future. We have serious obligations to those who came before us to make sure that they suffer as little as possible. Also, by helping them, we can not only improve our own lives, but also the lives of those glorious trillions which definitely, 100% absolutely exist in the future.

As a result, it is morally imperative that we invest all of our available resources into inventing time travel in order to go back and improve the lives of our ancestors.

Simply put, the past was a shitty place to live. Life expectancies were short, the conditions were usually miserable, and most people lived in what we now know to be crushing poverty. Until about the 19th century, the majority of people died of infectious or communicable disease. Now, especially in richer countries, it’s a significant minority. Without access to electricity and petrochemicals, the human population collapsed during the last ice age. Hell, on the more prosaic front, they often just didn’t have enough to eat, and no one who died before July 29th, 2004 got to taste Mountain Dew Baja Blast.

By inventing time travel, we can alleviate this suffering and right these horrible moral wrongs. We can send penicillin back to cure the Black Death before it becomes a pandemic. We can send coal and mining equipment back to the ice age to ensure that over 90% of the human population doesn’t die. We can send boxes of modern fertilizer and bags of Nacho Cheese Doritos® Locos Tacos back to any population whose daily average calories dip below 2500 per person.

Not only will this alleviate suffering and swell the ranks of past humans, it will also benefit the future humans that longtermism already acknowledges matter just as much. By starting the exponential population growth curve earlier and smoothing out its dips, we can easily go from trillions of future humans to quadrillions. By sending back instructions on how to financialize grain futures and set up stock markets, we can kick-start economic prosperity and push current and future stock prices into the stratosphere. A little back-of-the-napkin math says that if we go back and teach Muhammad ibn Musa al-Khwarizmi, the inventor of Algebra, about corporations and stock markets in the early 9th century, the S&P 500 will be at about 1.8 decillion USD in 2026, rather than a mere 7700.

And those gains will just compound into the future, making our quadrillions of descendants unfathomably wealthy.

Of course, I know some of you will object that time travel is impossible. Unlike godlike super-intelligence that is guaranteed to arise out of scaling the IQ of LLMs upwards (a thing which is both certainly happening and also going to continue forever), we don’t even know if it’s possible to reverse the arrow of time. Much less do so in a way that lets us send information or resources back to our ancestors.

This is true enough, but we also don’t know that it’s impossible. Several smart people have made cases for time travel, such as Phil Dowe from the Australian National University. There are even physicists who believe that they can reverse time in small-scale quantum systems. They believe the theory is testable and if those tests are successful and scale up the way quantum computers or LLMs do, then time travel is only a matter of, well, time. (And money, of course).

Now, I admit that we live in a world of uncertainty (except for the fact that there will be trillions of future humans, that is without doubt), so we’ll take a trick from the Silicon Valley Rationalist community and express our belief in terms of probability. They call it Bayesian because they update whenever they hear an argument for or against, and since it’s updated, that makes it both scientific and epistemically humble. These Bayesian probabilities allow us to do a nice, objective expected value calculation.

After reading the abstracts and conclusions of several papers about time travel, I initially estimated about a 10% chance that it would eventually be possible to send information or resources backwards in time. Then, because 10% seemed suspiciously round and un-humble, I adjusted my Bayesian probability down to 8%.

But even with only an 8% chance, time travel is a much better longtermist investment. 0.08 of a quadrillion is still 80 trillion humans we expect to save in the future via this tack. And 0.08 of 1.9 decillion is several hundred nonillion dollars. Even with our modest prediction of success, it’s still looking pretty good.

In fact, you could be extra humble and stuff a couple more zeros into our P(TimeTravel)¹ and you’re still looking at hundreds of billions of lives saved and a few nonillion dollars added to just our current stock prices, not to mention those of our far future progeny, all of whom will no doubt be shareholders in several S&P-listed companies.

As you can see, the only moral choice is to stop all AI research and immediately invest all of our resources into time travel. Don’t worry, though, once we invent it, we can send all of the Claude source code and model weights back to ancient Athens and the Pythagoreans can get an early start on it for us.