You're not actually disagreeing with Harris. Crafting efficient lies that behave as you describe is hard, particularly on the spot during conversation. Practice helps, and having your interlocutor's trust can compensate for a lot of imperfections, but it's still a lot of work compared to just sharing everything you know
Hm, that gives me an idea: study lying as a computational complexity problem. Just as we can study how much computing power it takes to distinguish random data from encrypted data, we can study how much computing power it takes to formulate (self-serving) hypotheses that take too much effort to distinguish from the truth.
Just a thought...
(Scott Aaronson's paper opened my eyes on the subject.)
Here's the new thread for posting quotes, with the usual rules: