The public intellectual, as a person and ideal, has a long and storied history. Writing in venues like the New Republic and Commentary, such intellectuals were always expected to opine on a broad array of topics, from foreign policy to literature to economics. Yet in recent years a new kind of thinker has supplanted that archetype: the thought leader. Equipped with one big idea, thought leaders focus their energies on TED talks rather than highbrow periodicals.
How did this shift happen? In The Ideas Industry, Daniel W. Drezner points to the roles of political polarization,...