Isn't causality strictly a map of a world strictly governed by physical laws? If a billiard ball strikes another ball, causing it to move, that is just our way of describing the motions of the balls. And besides, the universe doesn't even split the world up into individual "objects" or "events," so how can causality really exist?

By the way, any physical system is defined not just by its positions, but by its derivatives and second derivatives as well (I believe this is enough to describe the complete state of a system?). So when you talk about frozen states in a timeless universe, they still have to have time derivatives (in our perception of them). In other words, a sequence of still claymation frames and continuous motion may produce the same movie, but they correspond to very different realities.

iwdw: there has been some thinking about the universe as an actual game of life, Steven Wolfram's New Kind of Science is the one that comes to mind, but I'm sure there are more reputable sources that he stole the idea from. I believe that this thinking runs into trouble with special relativity.

Speaking of which, has anyone ever attempted to actually model space as a graph of relationships between points, in a computer program? Something like the distance-configuration-space in the last post? It occurs to me that this could actually be a more robust representation for some purposes than just storing the xyz coordinates.

Eliezer: I actually have been getting the insights you speak of repeatedly throughout this series, and it's one of the reasons why I find it helpful to post comments - because it forces me to think through the ideas well enough to get their occasional mind-bendingness. It's also why I have continued reading despite all the what-is-Science business.

But I still think that the subjective time-like-ness of time, as well as the concept of causality, are all caused (ha-ha) by the universe starting out in a low-entropy state. So if you had a toy block universe in your hands, you would still see a direction in the block corresponding to time. There is no way to assign a meaningful distance in that direction for the whole universe because of the locality of physics, but the direction is global, isn't it?

But the main thing that's different about time is that it has a clear direction whereas the space dimensions don't. This is caused by the fact that the universe started out in a very low-entropy state, and since then has been evolving into higher entropy. I don't know if it's even possible to answer the question of why the universe started out the way it did -- it's almost like asking why anything exists at all. But whatever the reason, the universe is very uniform in its space dimensions, but very non-uniform in its time dimension.

Doesn't the Lorentz invariant already pretty much take care of the relativity of time? As long as we're using the Lorentz invariant, we're free to reparameterize the universe any way we want, and our description will be the same. So I don't see what this Barbour guy is going on about, it seems like standard physics. Whether you write your function f(x,t) or f(y) where y = g(x,t) or even just f(x) where t = h(x) is totally irrelevant to the universe. It's just another coordinate transformation just like translating the whole universe by ten meters to the left.

Now, if you have a new invariant to propose, THAT would amount to an actual change in the laws of physics.

By the way, when the best introduction to a supposedly academic field is works of science fiction, it sets off alarm bells in my head. I know that some of the best ideas come from sci-fi and yada, yada, but just throwing that out there. I mean, when your response to an AI researcher's disagreement is "Like, duh! Go read some sci-fi and then we'll talk!" who is really in the wrong here?

Likewise the fact that the human brain must use its full power and concentration, with trillions of synapses firing, to multiply out two three-digit numbers without a paper and pencil.

Some people can do it without much effort at all, and not all of them are autistic, so you can't just say that they've repurposed part of their brain for arithmetic. Furthermore, other people learn to multiply with less effort through tricks. So, I don't think it's really a flaw in our brains, per se.

Apropos of this, the Eliezer-persuading-his-Jailer-to-let-him-out thing was on reddit yesterday. I read through it and today there's this. Coincidence?

Anyway, I was thinking about the AI Jailer last night, and my thoughts apply to this equally. I am sure Eliezer has thought of this so maybe he has a clear explanation that he can give me: what makes you think there is such a thing as "intelligence" at all? How do we know that what we have is one thing, and not just a bunch of tricks that help us get around in the world?

It seems to me a kind of anthropocentric fallacy, akin to the ancient peoples thinking that the gods were literally giant humans up in the sky. Now we don't believe that anymore but we still think any superior being must essentially be a giant human, mind-wise.

To give an analogy: imagine a world with no wheels (and maybe no atmosphere so no flight either). The only way to move is through leg-based locomotion. We rank humans in running ability, and some other species fit into this ranking also, but would it make sense to then talk about making an "Artificial Runner" that can out-run all of us, and run to the store to buy us milk? And if the AR is really that fast, how will we control it, given that it can outrun the fastest human runners? Will the AR cause the human species to go extinct by outrunning all the males to mate with the females and replace us with its own offspring?

I think that I have only now really understood what Eliezer has been getting at with the past ten or so posts, this idea that you could be a scientist if you generated hypotheses using a robot controlled Ouija board. I think other readers have already said this numerous times, but this strikes me as terribly wrong.

First of all, good luck getting research funding for such hypotheses (and it wouldn't be fair to leave out funding from the description of Science if you're including institutional inertia and bias).

And I think we all know that in general, someone who used this method would never be able to get anywhere in academia, simply because they wouldn't be respected.

That, I think, teaches an important lesson. Individual scientists are not required to come up with correct or even plausible hypotheses because we all know that individual rationality is flawed. But the aggregate community of scientists and the people who fund them work together to evaluate the plausibility of a given hypothesis, and thereby effectively carry out the Bayesian analysis that Eliezer speaks of.

So one of many thousands of scientists can propose an utterly harebrained theory, and even spend his life on it if he wants, and it will barely register as a blip on the collective scientific radar. But when SR and GR were proposed, it was pretty much taken as a given that they were true, because they HAD to be true. I read somewhere that the experiment done by Eddington to verify the bending of light around the sun was far from accurate enough to actually be a verification of relativity. But it was still taken as a verification, because everyone was pretty much convinced anyway. And conversely, no matter how many experiments the cold fusion people do that show some unexpected effects, nobody takes them very seriously.

Now, you might say that this system is horribly inefficient, and many people say this on a regular basis. But here, the problem is simply that no individual human being can process that much information, and so the time it takes for a given data point to propagate through the community is very long. Of course, the internet helps, and if scientific journals were free, that would probably help also. But ultimately, I think this inefficiency is precisely the cost of a network evaluating all of the priors to find out the plausibility of a theory.

Of course, it also reduces a scientist to nothing more than a cog in a machine, and many people who want to be heroic can't deal with that. But in real life, no scientist is expected to evaluate his own hypothesis. They are expected to come up with a hypothesis, and try to verify it if they can get funding, and let the community decide to what extent the results are valid.

First, I think this can be said for any field: the textbooks don't tell you what you really need to know, because what you really need to know is a state of mind that you can only arrive at on your own.

And there are many scientists who do in fact spend time puzzling over how to distinguish good hypotheses from bad. Some don't, and they spend their days predicting what the future will be like in 2050. But they need not concern us, because they are just examples of people who are bad at what they do.

There is this famous essay: http://www.quackwatch.com/01QuackeryRelatedTopics/signs.html

And also this one: http://wwwcdf.pd.infn.it/~loreti/science.html

P(A&B)<=P(A), P(A|B)>=P(A)

Isn't this just ordinary logic? It doesn't really require all of probability theory. I believe that logic is a fairly uncontroversial element of scientific thought, though of course occasionally misapplied.