By “Cartesian” decision theory, I mean the kind that is standard outside LW, where the decision process that makes the decision is not part of the model of the world. The epitome of this is AIXI (or actually even better, its computable cousin, AIXI-tl), and I think discussions of AIXI are where I got the word “Cartesian” from in this context: AIXI is considering complete models of the whole outside world, but doesn’t understand that it’s own computations are produced by part of that world, so that e.g. it would be a bad idea to drop a hammer on its own head. This would make more sense if AIXI’s sensory input were radioed from the physical world into the Great Outer Beyond of souls, free will, and infinite computing power, and AIXI then radioed back the actions it wants to take, but there were no other interactions between the two worlds—hence the word “Cartesian”, as in Cartesian dualism.
So in the context under discussion here, a “world” is a full specification of the laws of physics and the full current physical state of the universe—from which you can compute all that will happen in the future… except that you additionally need to know the input that will get radioed in from the Outer Beyond, specified by your strategy.
By “Cartesian” decision theory, I mean the kind that is standard outside LW, where the decision process that makes the decision is not part of the model of the world. The epitome of this is AIXI (or actually even better, its computable cousin, AIXI-tl), and I think discussions of AIXI are where I got the word “Cartesian” from in this context: AIXI is considering complete models of the whole outside world, but doesn’t understand that it’s own computations are produced by part of that world, so that e.g. it would be a bad idea to drop a hammer on its own head. This would make more sense if AIXI’s sensory input were radioed from the physical world into the Great Outer Beyond of souls, free will, and infinite computing power, and AIXI then radioed back the actions it wants to take, but there were no other interactions between the two worlds—hence the word “Cartesian”, as in Cartesian dualism.
So in the context under discussion here, a “world” is a full specification of the laws of physics and the full current physical state of the universe—from which you can compute all that will happen in the future… except that you additionally need to know the input that will get radioed in from the Outer Beyond, specified by your strategy.
So it is a description rather than a name. Thank you.