[Question] What is an Evidential Decision Theory agent?

One thing that I’ve noticed when talking to people about decision theory is that there is a lot of confusion about what an evidential decision theory agent actually is. People have heard that it doesn’t smoke in Smoking Lesion and that it pays in X-Or Blackmail, but that is what it does. They may know that it doesn’t do Pearlean Graph surgery or differentiate correlation from causation in some sense, but that is what it is not. They may even know it calculates an expected value using the probability distribution P(O|S&A), but that is just a mathematical formalisation which anyone can quote without any real understanding. I’ve taken a stab at clarifying it in a few short-form posts, but people didn’t seem to find them very enlightening.

Even now, my understanding is still weaker than I’d like. Like I just spent over fifteen minutes thinking about whether it would be accurate to characterise it as an agent that is purely concerned with correlation with no notion of causation. I thought this would be accurate at first, but then I realised that under reasonable assumptions, an EDT agent wouldn’t expect buying a diamond necklace to increase its wealth. After all, it would be able to notice that an increase in wealth tends to precede buying such a necklace, but this pattern doesn’t occur in reverse. In other words, it tends to have at least some ability to model causation.

Anyway, it seems, to me at least, that it would be rather useful for someone to have a go at providing a clear explanation of what exactly it is.

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