The way EDT operates is to perform the following three steps for each possible action in turn:
Assume that I saw myself doing X.
Perform a Bayesian update on this new evidence.
Calculate and record my utility.
Ideal Bayesian updates assume logical omniscience, right? Including knowledge about logical fact of what EDT would do for any given input. If you know that you are an EDT agent, and condition on all of your past observations and also on the fact that you do X, but X is not in fact what EDT does given those inputs, then as an ideal Bayesian you will know that you’re conditioning on something impossible. More generally, what update you perform in step 2 depends on EDT’s input-output map, thus making the definition circular.
So, is EDT really underspecified? Or are you supposed to search for a fixed point of the circular definition, if there is one? Or does it use some method other than Bayes for the hypothetical update? Or does an EDT agent really break if it ever finds out its own decision algorithm? Or did I totally misunderstand?
Ideal Bayesian updates assume logical omniscience, right? Including knowledge about logical fact of what EDT would do for any given input.
Note that step 1 is “Assume that I saw myself doing X,” not “Assume that EDT outputs X as the optimal action.” I believe that excludes any contradictions along those lines. Does logical omniscience preclude imagining counterfactual worlds?
If I already know “I am EDT”, then “I saw myself doing X” does imply “EDT outputs X as the optimal action”. Logical omniscience doesn’t preclude imagining counterfactual worlds, but imagining counterfactual worlds is a different operation than performing Bayesian updates. CDT constructs counterfactuals by severing some of the edges in its causal graph and then assuming certain values for the nodes that no longer have any causes. TDT does too, except with a different graph and a different choice of edges to sever.
Ideal Bayesian updates assume logical omniscience, right? Including knowledge about logical fact of what EDT would do for any given input. If you know that you are an EDT agent, and condition on all of your past observations and also on the fact that you do X, but X is not in fact what EDT does given those inputs, then as an ideal Bayesian you will know that you’re conditioning on something impossible. More generally, what update you perform in step 2 depends on EDT’s input-output map, thus making the definition circular.
So, is EDT really underspecified? Or are you supposed to search for a fixed point of the circular definition, if there is one? Or does it use some method other than Bayes for the hypothetical update? Or does an EDT agent really break if it ever finds out its own decision algorithm? Or did I totally misunderstand?
Note that step 1 is “Assume that I saw myself doing X,” not “Assume that EDT outputs X as the optimal action.” I believe that excludes any contradictions along those lines. Does logical omniscience preclude imagining counterfactual worlds?
If I already know “I am EDT”, then “I saw myself doing X” does imply “EDT outputs X as the optimal action”. Logical omniscience doesn’t preclude imagining counterfactual worlds, but imagining counterfactual worlds is a different operation than performing Bayesian updates. CDT constructs counterfactuals by severing some of the edges in its causal graph and then assuming certain values for the nodes that no longer have any causes. TDT does too, except with a different graph and a different choice of edges to sever.