Why I’m Skeptical of Longtermism

James Brobin10 Aug 2026 15:19 UTC
12 points
4 comments3 min readEA link

Longtermism is the view that we have a moral obligation to make the far future better.

It is usually argued for on the basis of the following claims:

  1. Future people are morally important.

  2. The future will be vast in expectation.

  3. There are actions available to us today that can meaningfully influence the far future. (I.e. Preventing human extinction)

  4. Due to the size of humanity’s potential, the value of these actions’ effects will, in expectation, be very large.

These claims are usually based on the assumption that, based on our present understanding of the world, we are justified in believing:

  1. We can make predictions about the far future that are sufficiently accurate that we are justified in using them to guide our decision-making.

  2. There are actions available to us that can predictably influence the far future.

  3. Humanity will, in expectation, persist for millions, billions, or even trillions of years.

  4. Humanity will use a significant portion of these resources over this time to create whatever you consider morally good (or whatever actually is morally good.)

I think that this view initially has some appeal because we don’t normally think on these kinds of time scales. As such, if you’ve never really considered how long you think humanity will persist, it may seem pretty plausible that humanity will persist for eons.

That said, I’m quite skeptical of longtermism, and, in today’s post, I want to share three reasons why.

Reason #1: Our Confidence About Future Affairs Should Reduce Over Time

If I put a rock on the ground in the middle of nowhere, I can be fairly confident that it will be there the next day. If it’s quite heavy, I can reasonably expect that it will be there next year. But, no matter how heavy it is, I should have almost no confidence about where it will be a million years from now.

This is because the world is chaotic, and, as a result, the possibility space of future affairs is extraordinarily vast. Although we can reasonably expect that there will likely be some state of affairs as we go further out in time, we should also expect that we will know virtually nothing about what that state of affairs will look like.

I think this argument similarly applies to humanity’s history, and hence, also, its long-term future.

Thus far, human history has been extraordinarily chaotic. The profoundly complex interaction of social, political, environmental, economic, and circumstantial factors has determined what the present day looks like. And, if we were to travel back in time and alter starting conditions just slightly, it seems reasonable to expect that the world today would be completely different.

For instance, if Mesopotamia had been just a bit less fertile, it seems like Greece and the Roman Empire would have had very different religions, and, as a result, the world, today, would be unrecognizable. Similarly, if the distribution of power in Europe before World War I were slightly different, it seems like the current distribution of power globally would be vastly different than it is today.

Given this, it seems like we should also expect humanity’s future to be very chaotic such that slight changes in the world today create vast differences in how it looks in the future. And, if this is the case, then we should have no confidence whatsoever about what our far future will look like.

Reason #2: We’re Bad At Making Predictions About The Future

Now, even if I concede that humanity’s future will not be chaotic, it’s worth pointing out that we probably shouldn’t give any weight to our current predictions about the future given that, historically, we’ve been very bad at making predictions about the future.

I don’t think this claim needs particularly much justification given that, if we had oracle-like abilities for predicting the future, especially over long periods of time, we would know.

That said, it really is quite striking how bad people are at predicting the future. For instance, when the Founding Fathers created the US constitution, most of them didn’t expect the country to last more than fifty years. And, when the Nazis came to power, they expected to last for a millennium, calling themselves the “Thousand-Year Reich,” but, ultimately, their rule only lasted for twelve years.

If we can’t reliably make predictions about almost anything a hundred years out, I don’t think we should be able to make reliable predictions millions or billions of years out.

Reason #3: Even If Humanity Persists, It May Not Create A World We Would Approve Of

Longtermists often make the argument that, despite our cluelessness about the future, we should still assign at least some non-trivial probability to the chance that humanity will persist for millions of years. But, even if we do this, I don’t think it improves their argument very much since we don’t know whether future humans would create a world that we would approve of.

Currently, humans hold what we consider to be enlightened values as a result of an extraordinarily specific set of biological, environmental, and historical conditions, and, as a result of these values, we create what we consider to be a just world. Problematically, though, we don’t know what conditions future humans will live under so we don’t know how similar their values will be to ours.

For instance, as the result of globalization, digital interconnection, the establishment of human rights, and the widespread use of democracy, we’ve seen what we believe to be significant moral progress over the last century. But, if future humans don’t live under democracy, their values may shift in a direction that we would consider to be quite negative.

James Brobin10 Aug 2026 15:19 UTC
12 points
4 comments3 min readEA link