Benja: This breaks the implicit decision theoretic premise that your payoff depends only on the action you choose, not on the process you use to arrive at that choice
Correct! The next step in the argument, if you were going to formulate my timeless decision theory, is to describe a new class of games in which your payoff depends only on the type of decision that you make or on the types of decision that you make in different situations, being the person that you are. The former class includes Newcomb's Problem; the latter class further includes the conditional strategy of the Prisoner's Dilemma (in which the opponent doesn't just care whether you cooperate, but whether you cooperate conditional on their cooperation).
However, within this larger problem class, we don't care why you have the decision-type or strategy-type that you do - we don't care what ritual of cognition generates it - any more than Omega in Newcomb's Problem cares why you take only one box, so long as you do.
Though it may be important that the other player knows our strategy-type, which in turn may make it important that they know our ritual of cognition; and making your decision depend on your opponent's decision may require knowing their strategy-type, etc.
Followup to: The True Prisoner's Dilemma
For everyone who thought that the rational choice in yesterday's True Prisoner's Dilemma was to defect, a follow-up dilemma:
Suppose that the dilemma was not one-shot, but was rather to be repeated exactly 100 times, where for each round, the payoff matrix looks like this:
As most of you probably know, the king of the classical iterated Prisoner's Dilemma is Tit for Tat, which cooperates on the first round, and on succeeding rounds does whatever its opponent did last time. But what most of you may not realize, is that, if you know when the iteration will stop, Tit for Tat is - according to classical game theory - irrational.
Why? Consider the 100th round. On the 100th round, there will be no future iterations, no chance to retaliate against the other player for defection. Both of you know this, so the game reduces to the one-shot Prisoner's Dilemma. Since you are both classical game theorists, you both defect.
Now consider the 99th round. Both of you know that you will both defect in the 100th round, regardless of what either of you do in the 99th round. So you both know that your future payoff doesn't depend on your current action, only your current payoff. You are both classical game theorists. So you both defect.
Now consider the 98th round...
With humanity and the Paperclipper facing 100 rounds of the iterated Prisoner's Dilemma, do you really truly think that the rational thing for both parties to do, is steadily defect against each other for the next 100 rounds?