From The Left Side of History by Allen Guelzo in The Claremont Review of Books:

It was precisely the wide overlap in assumptions shared by Progressivism and its subsequent historians which blinded so many of them to Progressivism’s most fundamental premise, and turned histories of Progressivism into yet another strange case of the dog in the night (who does not bark because he sees no one strange enough to make him bark). Understand, Watson warns us at the outset, that “[t]he progressive idea, simply put, is that the principled American constitutionalism of fixed natural rights and limited and dispersed powers must be overturned and replaced by an organic, evolutionary model of the Constitution that facilitates the authority of experts dedicated to the expansion of the public sphere and political control, especially at the national level.” This fundamental “idea” opened into five major applications: 1) that “there are no fixed or eternal principles that govern,” 2) that “the state and its component parts are organic” and “involved in a struggle for never-ending growth,” 3) that “democratic openness and experimentalism…are the fertilizer of the organic state,” 4) that “the state and its components exist only in History,” and 5) that “some individuals stand outside this process…an elite class, possessed of intelligence as a method” who provide the messianic leadership needed to move the process smoothly along.