Anonymous asked: The new decision theory paper exists because the old TDT paper did not have any formalism at all. The not really new FDT is the obvious way to formalize the hand waving in the original TDT paper but otherwise there is no new content. I think the paper exists because they decided they should at least write down a formalism somewhere.

Huh, okay, that makes some sense.

In the comment thread on MIRI’s blog post announcing the paper, I found the following comment from Rob Bensinger, answering the question “How does this relate to TDT?”:

FDT is an improvement over TDT that adds updatelessness. FDT is similar to what people usually mean by “UDT” (though “UDT” has come to refer to a lot of different things over the years and is less well-defined). E.g., Wei Dai’s UDT 1.1 ( http://lesswrong.com/lw/1s5… ) is a particular version of FDT, with FDT as the umbrella category.

UDT 1.1 was a big improvement over TDT, but it wasn’t perfect (though it may be the best we’ve got), it built in some debatable assumptions (over and above what’s needed to show why TDT, CDT, and EDT don’t work), and it was somewhat harder to explain than TDT. FDT as presented here is agnostic about the weirdest parts of UDT 1.1, and is about as easy to explain as TDT.

I never really looked into UDT, so I don’t actually know what “updatelessness” means here, but I guess it distinguishes FDT from the original TDT.  Based on this comment, it looks like they are trying to specify a minimal set of desiderata that their new decision theory must satisfy, even if they don’t have the theory itself (i.e. don’t have a working algorithm completely free of hand-waving).

Anonymous asked: Where does the ship name “iodized salt” come from?

There’s an explanation here.  I only just realized that that post is hard to find because it’s tagged “#iodized salt” with a “z,” since it’s back before we standardized the spelling to “iodised.”  I’ve now tagged it with both spellings, so people should be able to find it more easily now.

birdblogwhichisforbirds asked: Okay, so for some reason in on of my Weird Coping Mechanism Rants Rob & I got hung up on the question of what if Jesus' central doctrine has been that nobody should buy a boat, and therefore no age of sail in Europe. Maybe a Chinese age of sail? Maybe a new religion would have transplanted Christianity faster? Have opinions on this random and absurd hypothetical, please and thank.

femmenietzsche:

Well, let’s see. The first question we need to ask is how this would affect the early history of Christianity. The Roman world was in large part a maritime one; a great deal of travel was by sea and Christianity was in part spread that way. We know, for instance, that the apostle Paul was shipwrecked off Malta at one point, while carrying out missionary activity. In principle, a ban on buying boats wouldn’t have a big impact on Christianity’s spread, since missionaries could travel on boats made by others. However, it’s possible that a clever emperor could ban ship owners from transporting Christians. That could hinder the spread of Christianity, but I doubt that it would be enough to stop it, except perhaps to marginal islands further afield.

(I’m assuming here that Christians can’t just do a simple legal workaround by having the boats be nominally in someone else’s name. If that were the case then the prohibition on boat buying would be entirely trivial and would only have a minimal effect on world history, thus negating the point of the counterfactual. And I’m assuming the prohibition is a bit broader than ownership - Christians are forbidden from doing boat-related things, though probably not just being passengers.)

But let’s say that Christianity nevertheless took over the Roman empire, perhaps at a slightly later date. Will there be any differences between this universe’s late classical Christendom and ours? I think so. Even back then, naval warfare was of considerable importance, and a state with no navies would be at a considerable disadvantage, probably such a disadvantage that sooner or later it would get conquered, if not wiped out completely. Even if naval battles aren’t usually key, you can’t just tie one hand behind your back permanently and not expect to lose ground as time goes on.

However, there may be workarounds. For comparison, think about how moneylending was severely restricted by the medieval church. Did that mean that no money was lent? No, it meant that that niche was filled by Jews instead. You could imagine something similar happening with boats/ships. If Christians couldn’t buy boats themselves, but were powerful enough to hire others who did own boats, then you could imagine a Christianity which is defended at sea by sailors who are Jewish or pagan.

This seems like a tenable situation to me. Lots of empires throughout history have had armies which were largely foreign, including Rome at times. I don’t know of any navies like that, but it wouldn’t surprise me if something similar happened at some point. Anyway, unlike praetorian guards or Mamluks, the navies by themselves would probably be unable to take over the Christian societies which employ them. You could have a culturally separate naval caste without worrying about them overthrowing you and your religion. Basically, some of the tribes from the area around the Roman empire would remain pagan, defending a population of Christian landlubbers.

But is this the same Christianity from our timeline? Again, not exactly. It’s a Christendom with a much larger and more powerful non-Christian contingent (fisherman and merchants too, not just soldiers), and it’s one that’s hampered militarily, however effective the workarounds are. It’s a Christendom which is less monolithic and less culturally threatening to pagans. This means that Christianity will be considerably less appealing to northern Europe. The kings of northern Europe basically converted to Christianity because it was profitable to do so. It let them integrate with the rest of Europe. In this alternate universe, that’s no longer the case. In fact, it might be much more profitable to remain pagan, and fill those essential economic and military niches for the southern, Christian society. So the spread of Christianity outside of the former Roman empire will be much more limited.

Which brings me to my real point: Vikings. Vikings, being maritime raiders, would be the least likely people in the world to convert to Christianity in this situation. To do so would basically wipe out their whole way of life. However, I think it’s unlikely that they would remain pagan or polytheistic forever. It’s not impossible, but we’ve seen time and again that proselytizing monotheisms can outcompete simpler, preliterate folk religions. So, if Vikings won’t become Christian, what will they become? One possibility is that the Norse religion itself will absorb Christian ideas (though not the ban on boats) and become a more “modern” faith. (This possibly happened a bit in our timeline as well. The story of Odin hanging on the World Tree may have been inspired by the crucifixion.)

But the other, more plausible option is Islam. (Or some comparable eastern faith which arose in this timeline.) The Vikings traveled far and wide and they had substantial encounters with the Muslim world, often via the Byzantine Empire. I find it very easy to imagine Vikings importing Islam from the Middle East, as a way to distinguish themselves from the Christian peasants whose towns they raid. That would, if anything, give them even more of an advantage over their prey, through religious unity.

In fact, I think it’s safe to assume that the Vikings will be considerably stronger in this universe either way, given that the Christian world will be weaker. Even in our timeline, the Vikings were strong enough and expansionist enough to reach Newfoundland. Just imagine how much stronger that expansionist drive would be if it were backed by a proselytizing religion like Islam. They would have both the means and the motivation to keep sailing further and further.

So what I’m saying is: Muslim Vikings would conquer America.

Well, not quite that simple, maybe. They would perhaps reach America at around the time they did (around 1000 CE), but it’s unlikely that they’d have the ability to conquer as much land as the Spanish. For one thing, their sailing technology would still be relatively primitive. For another thing, they’d mostly be going to Canada and the northern US, which was not a profitable region back then. The real money was made in the plantations of the Caribbean. Founding plantations would be a big leap for Vikings to make. So I’m not sure that they would have the incentives or the ability to conquer two continents like that. More likely they would just conquer portions of it.

Diseases would still spread to the Americas, but the native population might recover enough to resist conquest when Old World sailing technology improved enough for greater transatlantic travel, some generations later.

Unless, however, word spread from the Vikings to Muslim North Africa about this new land, in which case the Arabs might make conquests of their own, perhaps even rivaling those of Europeans in our timeline. Either way, Islam would likely become the dominant religion across much of North and South America, whether through conquest or through trading links (as in southeast Asia). The wealth from this trade would, of course, sooner or later be used to overrun Christian Europe.

And that’s why you want a religion with some flexibility.

1. oh my god

2. In case you’re curious where this specific hypothetical came from, well, Esther and I were watching this video (the key part is at 0:25):