> As far as AIXI is concerned, this is the definition of an "intelligent action": that which leads to the largest expected utility over the agent's lifetime.
No. Largest expected utility over the (weighted) set of all possible future timelines (i.e. hypotheses). AIXI chooses the action that gives the best average over the set of future timelines. But we only live in one timeline. Maybe an action that is very good, averaged over all possible futures, is very bad in our actual timeline?
Now we can think than an action that is good on average, maybe it is probably good in our real timeline, too. But the way AIXI gives weight to different future timelines is based on how short their MDL [1] is. Maybe this is not at all how real world works? Who knows.
A silly example: Maybe there are a lot of possible future timelines where things randomly explode. And maybe their MDL is actually shorter than for timelines where things stay stable. Then we produce a highly intelligent robot that does nothing else but seeks shelter in the nearest empty room. And this would be the "definition of intelligent action". (Defined as the maximized intelligent action over imagined future timelines where things mostly randomly explode.)
Btw, in NFL theorem, the averaging is over all possible datasets (and datasets usually describe something about past, not future), not over all possible explanations. (But yes, you can think that implicitly behind every dataset there is a multitude of world models which could have produced the dataset.)
No. Largest expected utility over the (weighted) set of all possible future timelines (i.e. hypotheses). AIXI chooses the action that gives the best average over the set of future timelines. But we only live in one timeline. Maybe an action that is very good, averaged over all possible futures, is very bad in our actual timeline?
Now we can think than an action that is good on average, maybe it is probably good in our real timeline, too. But the way AIXI gives weight to different future timelines is based on how short their MDL [1] is. Maybe this is not at all how real world works? Who knows.
A silly example: Maybe there are a lot of possible future timelines where things randomly explode. And maybe their MDL is actually shorter than for timelines where things stay stable. Then we produce a highly intelligent robot that does nothing else but seeks shelter in the nearest empty room. And this would be the "definition of intelligent action". (Defined as the maximized intelligent action over imagined future timelines where things mostly randomly explode.)
Btw, in NFL theorem, the averaging is over all possible datasets (and datasets usually describe something about past, not future), not over all possible explanations. (But yes, you can think that implicitly behind every dataset there is a multitude of world models which could have produced the dataset.)
[1] Minimum Description Length