So we have:
A new metaphor to Finally Explain The Brain;
“While Eby provides few references and no peer-reviewed experimental work to support his case [...]”
A self-help book: “Thinking things Done(tm) The Effortless way to Start, Focus and finally Finish...” (really, I did not make this up).
I’d say some more skepticism is warranted.
A ‘Machiavellian rationalist’ would only speak truths when in its in his/her own best interests, and lie when that is more useful.
However, I think Eliezer wants to be a ‘friendly rationalist’[1]. Then, speaking the truth becomes the optimal thing in many more cases. It could also make it harder to succeed in fields like trade, politics, war, where bluff, misrepresentations etc. are important. And what about ‘Daddy, do you like this drawing I spent three hours making for you?’
And sometimes lying seems simply the best choice—no matter what Kant thinks. The classical gestapo-knocks-on-door example comes to mind. The disutility of lying can be smaller than utility of saving other people’s life (as well as you own).
Truthfulness is something to aspire to, but it’s hard to be absolutist about it. I think being ‘friendly’[1] is a useful dividing line, even if it can be abused to rationalize away lies.
[1] with ‘friendly’ here I mean: ‘being nice to the rest of humanity determines your utility function in a significant way’