The best explanation of the firing of FBI director James Comey and of the subsequent investigation by special counsel and former FBI director Robert Mueller may just come from a social scientist who died years before President Trump took office.

When James Q. Wilson died in 2012, he was remembered primarily for his influential 1982 Atlantic article with George Kelling, “Broken Windows: The Police And Neighborhood Safety,” advocating police tactics focused on maintaining order and reducing fear.

It turns out, though, that Wilson — whose colleagues in the government department at Harvard included Henry Kissinger and Daniel Patrick Moynihan — also wrote a whole book about the FBI.

That book, The Investigators: Managing FBI And Narcotics Agents, was published in 1978 by Basic Books and funded in part by a grant from Irving Kristol’s company, National Affairs, Inc. It is based on in part on Professor Wilson’s personal experience as an adviser to FBI director Clarence Kelley, who served between 1973 and 1978.

Its insights relevant to Messrs. Comey and Mueller come in a chapter considering the motivation of FBI executives, and of government officials in general. Wilson writes, “In my view, it is the desire for autonomy, and not for large budgets, new powers, or additional employees, that is the dominant motive of public executives.”

What does Wilson mean by “autonomy”? His book explains, “An agency is autonomous to the degree it can act independently of some or all of the groups that have the authority to constrain it.” Autonomy comes “by acquiring sufficient good will and prestige as to make attacks on oneself or one’s agency costly for one’s critics.”

This craving for autonomy applies not only at the executive level but also to front-line investigators, Wilson writes: “A detective wants, above all else, to be left alone and to be backed up.”

For much of its history, Wilson writes, the FBI “enjoyed an almost unparalleled degree of autonomy.” Wilson describes it as “extraordinary autonomy.”

The nice thing about this “autonomy” theory of the FBI is that it potentially explains both the bureau’s leaks about Hillary Clinton in 2016 and its reaction to President Trump in 2017 and 2018.

Remember, notwithstanding all the talk of anti-Trump texts by FBI agent Peter Strzok and FBI lawyer Lisa Page, Hillary Clinton has blamed Comey for her loss in the 2016 election. FBI leaks and public statements about investigations into Mrs. Clinton’s emails and the Clinton Foundation helped keep those stories in front of the electorate, especially after President Clinton’s 20-minute meeting with President Obama’s attorney general, Loretta Lynch, aboard her government airplane on a Phoenix runway.

The FBI is part of the Justice Department, which means that Mrs. Lynch at least theoretically was Mr. Comey’s boss. Autonomy, though, means not really being accountable to any boss. Mr. Comey has told Congress that the Bill Clinton-Loretta Lynch airplane meeting contributed to his decisions to issue public statements about the email investigation during the presidential campaign.

Similarly, the Trump-Comey relationship cratered after Mr. Comey apparently felt pressure from President Trump to ease off an investigation of Mr. Trump’s national security adviser, Michael Flynn, and to announce that Mr. Trump was not being investigated for colluding with Russia.

Mr. Mueller’s investigation is being described as a defense of democracy, or as a defense of the rule of law, or as an investigation into possible obstruction of justice or a coverup. After I read Wilson’s book, though, what the Mueller investigation looked like above all was precisely an effort by the FBI to defend its “extraordinary autonomy.”

“Autonomy” of the FBI might have certain advantages. It would prevent politically motivated meddling into criminal investigations, the same way that the “independence” of the Federal Reserve prevents politically motivated interference with interest rates.

A fully autonomous FBI, though, is inconsistent with Article 2 of the U.S. Constitution, which states, “The executive power shall be vested in a President of the United States of America.” Even if FBI directors such as Messrs. Comey or Mueller might prefer to operate without guidance from presidents or without guidance from attorneys general appointed by presidents, such a set-up would render the FBI unaccountable. Governments, the Declaration of Independence says, derive their just powers from the consent of the governed. Presidents Obama and Trump were elected. No one elected Comey or Mueller.

Wilson concludes his book with a warning. There have been, he writes, powerful law enforcement agencies in the world that operated without the constraints of political superiors or of public opinion. The record of such authoritarian secret police forces, “judged by the test of human liberty, is not promising.”