One of the things I admire about the profession of history is that there are no admissions requirements. Like being a novelist or a member of Congress, the door is open to almost anyone who wants to try their hand at the art or craft. In a world of an increasingly specialized division of professional labor, that is a relatively rare and special thing. Though I teach in a law school, for example, I would be in trouble if I tried to pass myself off as a lawyer. Though I could perhaps irritatingly refer to myself as a doctor owing to my Ph.D., if I tried writing medical treatises, they would be ignored. Though I dabble a bit in economic history, if I started calling myself an economist, I would certainly be reproached. But while there is a rigorous, heavily-credentialed, and well-established historical profession in the United States, the policing of disciplinary boundaries has not been its main priority. In fact, professional historians are marvelously ecumenical in welcoming others and outsiders to their field of study. Indeed, one of the most prestigious Ph.D. dissertation prizes in the United States is named after Allan Nevins-a journalist with a Masters degree in English who became one of the most widely admired of American historians. Barbara Tuchman, David McCollough, and many other Pulitzer Prize winners have followed in this venerable tradition. Historians might mutter privately when yet another journalist formally proclaims him- or herself a "Presidential historian" on CNN, but for the most part the reaction of professional historians to the expansion of their ranks in all possible directions is let a thousand flowers bloom. The house of history has many mansions.
Novak, William J. "Constitutional Theology: The Revival of Whig History in American Public Law." Michigan State Law Review 2010, no. 3 (2010): 623-62.