The argument we're (not quite) having here -- and to which Adam
Hochschild in Historically Speaking makes another important
contribution -- concerns a series of rich and timeless questions: what exactly is a historian? Should the term be applied only to those who possess doctoral degrees and publishing histories, or are historians a more broad and multifaceted group? Is everyone a historian, as Carl Becker famously argued? And assuming we can define the "wheat" and the "chaff," what separates the two? What does the "trained" historian have to offer that the "amateur" does not, or vice versa?
Good questions all. Let me start with what historians are not.
Historians are not theorists, though they may entertain certain theories in the course of interpreting an event they do not begin with answers as does a theorist but with questions. Questions they try to answer with research and evidence because history, while not a science, is an empirical discipline. Historians are not poets, they do not aim to create sweeping, romantic, myths, though like anyone else, historians admire mythic ideals but their task is to reveal where reality may have fallen short. Historians are not social scientists, though they sometimes borrow their tools; nor are they economists constructing abstract models hoping to predict events. A historian who tries to predict what will happen based upon the past is engaging in futurism, a very different and more difficult art.
None of this is meant to disparage political scientists, poets, economists, sociologists, anthropologists, authors of historical fiction or futurists. They all do worthy and interesting things, it's just that their work cannot properly be called "history". A historian is someone who tries to cogently explain what really happened, based upon the best evidence available; amateur or professional status matters less than skill, persistence and intellectual integrity in pursuing this task.
Historians have a varied set of skills. They are researchers, at times, detectives. They must consume and accurately recall vast amounts of historigraphical literature. Historians must think analytically foremost but also intuitively and sometimes, toward a synthesis. They must communicate clearly with the spoken and written word; and they must be teachers, literally in a classroom or in the larger sense of writing history to educate society. Few historians excel equally well at all of these different aspects but most good historians are strong or even exemplary in many of them.
In regard to the respective virtues of professional vs. "amateur" or "popular" historians ( many popular historians are or were also academics - Howard Zinn, Stephen Ambrose, Niall Ferguson and so on) it is important to recognize that they write for different audiences. Popular or amateur historians write for the intelligent reading public while academic historians write primarily for other academic historians. This is not a slam on profesional scholars but a recognition of differences in scope, scale and level of historical knowledge between the two groups of readers.
The public is not well prepared to handle or comment upon historical monographs of an esoteric or technical nature, only other specialists can do that. Nor are historians who have spent most of their career in a very rarefied subfield - say researching currency fluctuations in the Spanish Netherlands during the early modern period or Women's social status in the Caribbean during the late Colonial era - well positioned to write a panoramic history of Western civilization, of the history of technology or similarly big picture subjects desired by the layman who wants to "read some history". At least not without a major time investment.
The relationship between academic and popular/amateur historians is an interdependent one; the former are usually creating the monographic bricks with which the latter build their sweeping and entertaining literary edifices while popular historians "hook" readers into studying history more deeply - perhaps deeply enough to become a professional historian! One is not "better" than the other, simply different with distinct objectives.
The door of history is open to anyone - you simply need to walk through it.