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.