I'm listening to Dawkins' The God Delusion, and he talks quite a bit about the Anthropic Principle. Can someone summarize it in plain english?

The Anthropic Principle refers to any number of basic ideas suggesting that human life was a long shot to arise in a universe with our physical laws, so that the universe must have been "fine-tuned" for life.

The way that most non-scientists/philosophers/historians of science use it is generally sophistry and bad teleology in my experience.

Dawkins seems to speak favorably of it. I thought his point was that human life could only exist because of these favorable conditions, so the question of probability is moot.

I think you goofed that up.

http://en.wikipedia.org/wiki/Anthropic_principle

When Christians talk about alternate universes where rational life can exist we're called superstitious idiots.

Glad science is catching finally up.

You are mixing up assuming a multiverse with hypothesising alternate universes.

If you actually read the article you'll note that multiverse gets critizised on the same tangent as intelligent design.

If anybody is confused by the difference between hypothesising alternate universe and multiverse models consider the difference between these two:

1. Imagine what will happen if you never look for cars when you cross the road.
2. Assume there is a universe where you never look for cars when you cross the road.

1 serves a model purpose, 2 is superstitious idiocy.

I thought the anthropic principle was essentially a refutation of the fine-tuned universe theory

Anthropic principle is the idea that things are the way they are because we can observe them. A lot of constants in nature (things like charge or mass of electron or gravitational constant) appear to be fine tuned in such a way that if we changed those a little bit there would be no stars, or no atoms, or no large molecules. This is taken to be an obstruction to life and it is said that we observe such fine tuning simply because we exist, i.e. if things were different, there would not be us (or any other intelligent life) to observe those differences.

There are a lot of holes in the above idea and its logic which I can tell you about if you're interested, but suffice it to say that the anthropic principle is NOT accepted by the mainstream scientific community. One of the reasons for that is (at least as of right now) it has 0 predictive power and as such is completely useless.

Anthropic thinking is clearly problematic when talking about the universe as a whole but it is clearly useful in talking about properties of Earth and other planets. We clearly are not just on some random place in the universe and it may very well be that the Earth (and our solar system) is very, very peculiar.

No, I think it's a version of it:
http://en.wikipedia.org/wiki/Fine-tuned_Universe
Of course, that's making the assumption people on wikipedia know whereof they speak.

The fine tuning argument seems to me to be asking a question with knowledge as though you were ignorant of that knowledge. Is this a problem? Maybe.

Suppose I hypothesize a person, Steve Brandtley (I just made that up), who will be born in 2017, will go to East Caesar Middle School, will marry a girl named Lindsay Madsen, have two sons, both of whom are named Paul, etc. I could provide many details about this hypothetical person's life, then ask the question: will he exist? Clearly the probability of this is remote.

I could, then, pretend to go back in time to 1920 and "hypothesize" a person named David Sklansky, and go on to provide the details of his life. In ignorance, the probability that he will exist is zero, but of course know this is not the case. The fine tuning argument (OK, not exactly, but a similar argument) concludes that David Sklansky either does not exist, or was created by divine intervention.

The anthropic principle says that we need to take into account our existence and ability to ask the question. In the example above, in order to reach the fallacious conclusion, we need to ask a question that requires information from the present, but restrict those answering the question to information available in 1920.

As an aside, something unrelated that has always bothered me about fine tuning arguments is the presumption that life (in particular) requires atoms, electrons, and what have you. Self assembly does not seem like it should be restricted to only the laws of our universe; in hypothetical universes where atoms as we know them are not stable, how can we say whether or not matter will self assemble in some other way, eventually leading to organization and self replication along an entirely different path? Perhaps these beings are at this very moment hypothetically scoffing at the idea of life in a universe such as ours.