Julian: "You have to un-assume the decision before you stand any chance of clear thought."
Of course the decision-theoretic logic of this is unassailable, but I continue to worry that the real-world application to humans is nontrivial.
Here, I have a parable. Suppose Jones is a member of a cult, and holds it as a moral principle that it is good and right and virtuous to obey the Great Leader. So she tries to obey, but feels terrible about failing to obey perfectly, and she ends up having a nervous breakdown and removing herself from the cult in shame. Then, afterwards, as a defensive emotional reaction, she adopts an individualist philosophy and comes up with all sorts of clever arguments to the effect that the Great Leader isn't special at all and really no one has any duty to obey or even listen to her!
So then Jones reads "The Bottom Line," and realizes her adoption of individualism wasn't rational, and was simply a reaction to having been hurt so badly. If she had only been better at obeying the Great Leader, then, as a matter of (subjunctive) fact, she never would have come up with all those clever arguments, and wouldn't have found them convincing if someone else had told them to her. At this point, as rationalists, we advise Jones to clear her mind, unassume her decision to leave the cult, and reëvaluate the matter cleanly. But this advice might be underspecified: if she is supposed to reëvaluate her choice using her current morality, the decision is obvious: stay free. If she is supposed to reëvaluate using her original cult-morality, the decision is obvious: crawl back to the Great Leader, begging for forgiveness.
You can't reset yourself to a state a perfect emptiness; you have to reset yourself to something. Nor can you reset yourself to a state of perfect emptiness in order to decide what to reset yourself to; that's just an infinite regress.
I guess the best answer I can give to someone in such a dilemma (the answer I give myself) is to say, "Rational agents act to preserve their current goal system; my past self was confused, I cannot be bound by the terms of her confusion; I can only act from who I am, now, what I want, now."
But then that sounds like saying that the principle of the bottom line doesn't apply across morality changes. Which is a little suspicious.
Followup to: The Bottom Line
A recent conversation reminded me of this simple, important, and difficult method:
When someone asks you "Why are you doing X?",
And you don't remember an answer previously in mind,
Do not ask yourself "Why am I doing X?".
For example, if someone asks you
"Why are you using a QWERTY keyboard?" or "Why haven't you invested in stocks?"
and you don't remember already considering this exact question and deciding it,
do not ask yourself "Why am I using a QWERTY keyboard?" or "Why aren't I invested in stocks?"
Instead, try to blank your mind - maybe not a full-fledged crisis of faith, but at least try to prevent your mind from knowing the answer immediately - and ask yourself:
"Should I do X, or not?"
Should I use a QWERTY keyboard, or not? Should I invest in stocks, or not?
When you finish considering this question, print out a traceback of the arguments that you yourself considered in order to arrive at your decision, whether that decision is to X, or not X. Those are your only real reasons, nor is it possible to arrive at a real reason in any other way.
And this is also writing advice: because I have sometimes been approached by people who say "How do I convince people to wear green shoes? I don't know how to argue it," and I reply, "Ask yourself honestly whether you should wear green shoes; then make a list of which thoughts actually move you to decide one way or another; then figure out how to explain or argue them, recursing as necessary."