I would cooperate with you if I couldn't distinguish my code from yours, even if there might be minor differences, even in a one-shot case, because the best guess I would have of what you would do is that you would do the same thing that I do.

But since you're making it clear that your code is quite different, and in a particular way, I would defect against you.

Even if you're playing against a clone, you can distinguish the copies by where they are in space and so on. You can see which side of the room you are on, so you know which one you are. That means one of you can get utility without the other one getting it.

People don't actually have the same code, but they have similar code. If the code in some case is similar enough that you can't personally tell the difference, you should follow the same rule as when you are playing against a clone.

Yes. The universe is deterministic. Your actions are completely predictable, in principle. That's not unique to this thought experiment. That's true for every thing you do. You still have to make a choice. Cooperate or defect?

I'd go so far as to say that anyone who advocates cooperating in a one-shot prisoners' dilemma simply doesn't understand the setting. By definition, defecting gives you a better outcome than cooperating. Anyone who claims otherwise is changing the definition of the prisoners' dilemma.

I think this is correct. I think the reason to cooperate is not to get the best personal outcome, but because you care about the other person. I think we have evolved to cooperate, or perhaps that should be stated as we have evolved to want to cooperate. We have evolved to value cooperating. Our values come from our genes and our memes, and both are subject to evolution, to natural selection. But we want to cooperate.

So if I am in a prisoner's dilemma against another human, if I perceive that other human as "one of us," I will choose cooperation. Essentially, I care about their outcome. But in a one-shot PD defecting is the "better" strategy. The problem is that with genetic and/or memetic evolution of cooperation, we are not playing in a one-shot PD. We are playing with a set of values that developed over many shots.

Of course we don't always cooperate. But when we do cooperate in one-shot PD's, it is because, in some sense, there are so darn many one-shot PD's, especially in the universe of hypotheticals, that we effectively know there is no such thing as a one-shot PD. This should not be too hard to accept around here where people semi-routinely accept simulations of themselves or clones of themselves as somehow just as important as their actual selves. I.e. we don't even accept the "one-shottedness" of ourselves.

If I'm playing my clone, it's not clear that even saying that I'm making a choice is well-defined. After all, my choice will be what my code dictates it will be. Do I prefer that my code cause me to accept? Sure, but only because we stipulated that the other player shares the exact same code; it's more accurate to say that I prefer my opponent's code to cause him to defect, and it just so happens that his code is the same as mine.

I think you are making this more complicated than it needs to be. You don't need to worry about your code. All you need to know that it's an exact copy of you playing. And that he will make the same decision you do. No matter how hard you think about your "code" or wish he would make a different choice, he will just do the same thing about you.

In real life, my code is not the same as my opponent's, and when I contemplate a decision, I'm only thinking about what I want my code to say. Nothing I do changes what my opponent does; therefore, defecting is correct.

In real games with real humans, yes, usually. As I said, I don't think these cases are common enough to worry about. But I'm just saying they exist.

But it is more general than just clones. If you know your opponent isn't exactly the same as you, but still follows the same decision algorithm in this case, the principle is still valid. If you cooperate, he will cooperate. Because you are both following the same process to come to a decision.

the only time I'd ever want to cooperate in a one-shot prisoners' dilemma was if I thought my decision could affect my opponent's decision.

Well there is no causal influence. Your opponent is deterministic. His choice may have already been made and nothing you do will change it. And yet the best decision is still to cooperate.

You're confusing correlation with causation. Different players' decision may be correlated, but they sure as hell aren't causative of each other (unless they literally see each others' code, maybe).

Causation isn't necessary. You're right that correlation isn't quite sufficient, though!

What's needed for rational cooperation in the prisoner's dilemma is a two-way dependency between A and B's decision-making. That can be because A is causally impacting B, or because B is causally impacting B; but it can also occur when there's a common cause and neither is causing the other, like when my sister and I have similar genomes even though my sister didn't create my genome and I didn't create her genome. Or our decision-making processes can depend on each other because we inhabit the same laws of physics, or because we're both bound by the same logical/mathematical laws -- even if we're on opposite sides of the universe.

(Dependence can also happen by coincidence, though if it's completely random I'm not sure how'd you find out about it in order to act upon it!)

The most obvious example of cooperating due to acausal dependence is making two atom-by-atom-identical copies of an agent and put them in a one-shot prisoner's dilemma against each other. But two agents whose decision-making is 90% similar instead of 100% identical can cooperate on those grounds too, provided the utility of mutual cooperation is sufficiently large.

For the same reason, a very large utility difference can rationally mandate cooperation even if cooperating only changes the probability of the other agent's behavior from '100% probability of defection' to '99% probability of defection'.

Calling this source code sharing, instead of just "signaling for the purposes of a repeated game", seems counter-productive.

I disagree! "Code-sharing" risks confusing someone into thinking there's something magical and privileged about looking at source code. It's true this is an unusually rich and direct source of information (assuming you understand the code's implications and are sure what you're seeing is the real deal), but the difference between that and inferring someone's embarrassment from a blush is quantitative, not qualitative.

Some sources of information are more reliable and more revealing than others; but the same underlying idea is involved whenever something is evidence about an agent's future decisions. See: Newcomblike Problems are the Norm

Yes, I agree that in a repeated game, the situation is trickier and involves a lot of signaling. The one-shot game is much easier: just always defect. By definition, that's the best strategy.

If you and the other player have common knowledge that you reason the same way, then the correct move is to cooperate in the one-shot game. The correct move is to defect when those conditions don't hold strongly enough, though.

You're confusing correlation with causation. Different players' decision may be correlated, but they sure as hell aren't causative of each other (unless they literally see each others' code, maybe). [...] The one-shot game is much easier: just always defect. By definition, that's the best strategy.

Imagine you are playing against a clone of yourself. Whatever you do, the clone will do the exact same thing. If you choose to cooperate, he will choose to cooperate. If you choose to defect, he chooses to defect.

The best choice is obviously to cooperate.

So there are situations where cooperating is optimal. Despite there not being any causal influence between the players at all.

I think these kinds of situations are so exceedingly rare and unlikely they aren't worth worrying about. For all practical purposes, the standard game theory logic is fine. But it's interesting that they exist. And some people are so interested by that, that they've tried to formalize decision theories that can handle these situations. And from there you can possibly get counter-intuitive results like the basilisk.

It sounds like you have a different model of Eliezer (and of how well-targeted 'lashing out' usually is) than I do. But, like I said to V_V above:

According to Eliezer, he had three separate reasons for the original ban: (1) he didn't want any additional people (beyond the one Roko cited) to obsess over the idea and get nightmares; (2) he was worried there might be some variant on Roko's argument that worked, and he wanted more formal assurances that this wasn't the case; and (3) he was just outraged at Roko. (Including outraged at him for doing something Roko thought would put people at risk of torture.)

The point I was making wasn't that (2) had zero influence. It was that (2) probably had less influence than (3), and its influence was probably of the 'small probability of large costs' variety.

Defecting gives you a better outcome than cooperating if your decision is uncorrelated with the other players'. Different humans' decisions aren't 100% correlated, but they also aren't 0% correlated, so the rationality of cooperating in the one-shot PD varies situationally for humans.

Part of the reason why humans often cooperate in PD-like scenarios in the real world is probably that there's uncertainty about how iterated the PD is (and our environment of evolutionary adaptedness had a lot more iterated encounters than once-off encounters). But part of the reason for cooperation is probably also that we've evolved to do a very weak and probabilistic version of 'source code sharing': we've evolved to (sometimes) involuntarily display veridical evidence of our emotions, personality, etc. -- as opposed to being in complete control of the information we give others about our dispositions.

Because they're at least partly involuntary and at least partly veridical, 'tells' give humans a way to trust each other even when there are no bad consequences to betrayal -- which means at least some people can trust each other at least some of the time to uphold contracts in the absence of external enforcement mechanisms. See also Newcomblike Problems Are The Norm.

Like, the same utility as is gained by any other discussion on LW, pretty much.

Not every discussion on LW has the same utility.

You engage in a pattern of simplifying the subject and then complaining that your flawed understanding doesn't make sense.

Sure, but you're the one that was going on about the importance of the mindset and culture

LW doesn't have a culture with habitual banning discussion. Claiming that it has it is wrong.

I'm claiming that particular actions of Eliezer come out of being concerned about safety. I don't claim that Eliezer engages in habitual banning on LW because of those concerns.

It's a complete strawman that you are making up.