I should point out that the natural tendency for civilizations to fall appears to apply to subsets of the human civilization, rather than the entirety of humanity historically. While locally catastrophic, these events were not existential, as humanity survived and recovered.

I'd also argue that the collapse of a civilization requires far more probabilities to go to zero and has greater and more complex causal effects than all time machines just failing to work when tried.

And, the reality is that at this time we do not know if the Non-Cancel Principle is true or false, and whether or not the universe will prevent time travel. Given this, we face the dilemma that if we precommit to not developing time travel and time travel turns out to be possible, then we have just limited ourselves and will probably be outcompeted by a civilization that develops time travel instead of us.

Ah, that makes sense! Thanks for the clarification.

Why would the only way to prevent timeline collapse be to prevent civilizations from achieving black hole-based time travel? Why not just have it so that whenever such time travel is attempted, any attempts to actually change the timeline simply fail mysteriously and events end up unfolding as they did regardless?

Like, you could still go back as a tourist and find out if Jesus was real, or scan people's brains before they die and upload them into the future, but you'd be unable to make any changes to history, and anything you did would actually end up bringing about the events as they originally occurred.

I also don't see how precommitting to anything will escape the "curse". The universe isn't an agent we can do acausal trade with. Applying the Anthropic Principle, we either are not the type of civilization that will ever develop time travel, or there is no "curse" that prevents civilizations like ours from developing time travel. Otherwise, we already shouldn't exist as a civilization.

So, it seems like most of the existential risks from time travel are only if the Non-Cancel Principle you described is false? It also seems like the Non-Cancel Principle also prevents most time paradoxes, so that seems like strong evidence towards it being true?

It seems like the Non-Cancel Principle would lead to only two possible ways time travel could go about. Either everything "already happened" and so time travel can only cause events to happen as they did (i.e. Tenet), meaning no actual changes or new timelines are possible (no free will), or alternatively, time travel branches the timeline, creating new timelines in a multiverse of possible worlds (in which case, where did the energy for this timeline come from if Conservation of Energy holds?).

I find the latter option more interesting for science fiction, but I think the former probably makes more sense from a physics perspective. I would really like to be wrong on this though, because useful time travel would be really cool and possibly the most important and valuable technology that one could have (that or ASI).

Anyway, interesting write up! I've personally spent a lot of time thinking about time travel and its possible mechanics, as it's a fascinating concept to me.

P.S. This is Darklight from Less Wrong.

I mean, that innate preference for oneself isn't objective in the sense of being a neutral outsider view of things. If you don't see the point of having an objective "point of view of the universe" view about stuff, then sure, there's no reason to care about this version of morality. I'm not arguing that you need to care, only that it would be objective and possibly truth tracking to do so, that there exists a formulation of morality that can be objective in nature.

I guess the main intuitional leap that this formulation of morality takes is the idea that if you care about your own preferences, you should care about the preferences of others as well, because if your preferences matter objectively, theirs do as well. If your preferences don't matter objectively, why should you care about anything at all?

The principle of indifference as applied here is the idea that given that we generally start with maximum uncertainty about the various sentients in the universe (no evidence in any direction about their worth or desert), we should assign equal value to each of them and their concerns. It is admittedly an unusual use of the principle.

You could argue that if moral realism is true, that even if our models of morality are probably wrong, you can be less wrong about them by acquiring knowledge about the world that contains relevant moral facts. We would never be certain they are correct, but we could be more confident about them in the same way we can be confident about a mathematical theory being valid.

I guess I should explain what my version of moral realism would entail.

Morality to my understanding is, for a lack of a better phrase, subjectively objective. Given a universe without any subjects making subjective value judgments, nothing would matter (it's just a bunch of space rocks colliding and stuff). However, as soon as you introduce subjects capable of experiencing the universe and having values and making judgments about the value of different world states, we have the capacity to make "should" statements about the desirability of given possible world states. Some things are now "good" and some things are now "bad", at least to a given subject. From an objective, neutral, impartial point of view, all subjects and their value judgments are equally important (following the Principle of Indifference aka the Principle of Maximum Entropy).

Thus, as long as anyone anywhere cares about something enough to value or disvalue it, it matters objectively. The statement that "Alice cares about not feeling pain" and its hedonic equivalent "Alice experiences pain as bad" is an objective moral fact. Given that all subjects are equal (possibly in proportion to degree of sentience, not sure about this), then we can aggregate these values and select the world state that is most desirable overall (greatest good for the greatest number).

The rest of morality, things like universalizable rules that generally encourage the greatest good in the long run, are built on top of this foundation of treating the desires/concerns/interests/well-being/happiness/Eudaimonia of all sentient beings throughout spacetime equally and fairly. At least, that's my theory of morality.

So, regarding the moral motivation thing, moral realism and motivational internalism are distinct philosophical concepts, and one can be true without the other also being true. Like, there could be moral facts, but they might not matter to some people. Or, maybe people who believe things are moral are motivated to act on their theory of morality, but the theory isn't based on any moral facts but are just deeply held beliefs.

The latter example could be true regardless of whether moral realism is true or not. For instance, the psychopath might -think- that egoism is the right thing to do because their folk morality is that everyone is in it for themselves and suckers deserve what they get. This isn't morality as we might understand it, but it would function psychologically as a justification for their actions to them (so they sleep better at night and have a more positive self-image) and effectively be motivating in a sense.

Even -if- both moral realism and motivational internalism were true, this doesn't mean that people will automatically discover moral facts and act on them reliably. You would basically need to have perfect information and be perfectly rational for that to happen, and no one has these traits in the real world (except maybe God, hypothetically).

Ah, good catch! Yeah, my flavour of moral realism is definitely naturalist, so that's a clear distinction between myself and Bentham, assuming you are correct about what he thinks.

I'll admit I kinda skimmed some of Bentham's arguments and some of them do sound a bit like rhetoric that rely on intuition or emotional appeal rather than deep philosophical arguments.

If I wanted to give a succinct explanation for my reasons for endorsing moral realism, it would be that morality has to do with what subjects/sentients/experiencers value, and these things they value, while subjective in the sense that they come from the perceptions and judgments of the subjects, are objective in the sense that these perceptions and in particular the emotions or feelings experienced because of them, are true facts about their internal state (i.e. happiness and suffering, desires and aversions, etc.). These can be objectively aggregated together as the sum of all value in the universe from the perspective of an impartial observer of said universe.