He introduces the idea of a third cohort in an aside: “(There is a partly-formed attempt to spin off a Grey Tribe typified by libertarian political beliefs, Dawkins-style atheism, vague annoyance that the question of gay rights even comes up, eating paleo, drinking Soylent, calling in rides on Uber, reading lots of blogs, calling American football ‘sportsball’, getting conspicuously upset about the War on Drugs and the NSA, and listening to filk—but for our current purposes this is a distraction and they can safely be considered part of the Blue Tribe most of the time.)”