We may be sure that the “separation of powers” doctrine is of no interest to the vulgar egotist currently residing in the White House, which happens to be undergoing the most glorious renovation the world has ever known. Or so we hear. But it stands to reason that the doctrine is vital to personal liberty. No imagination is needed to understand what concentrated political power is likely to mean for the individual and society.

The name most closely associated with the separation of powers is Charles Louis de Secondat, baron de La Brède et de Montesquieu (1689-1755), a judge, philosopher, and historian whose 1748 book, The Spirit of Law, sometimes called The Spirit of the Law[s], heavily influenced the founders of the United States and the framers of the U.S. Constitution. Living in a censorial regime, Montesquieu originally published the work anonymously.

I won’t attempt to divine what Montesquieu really thought about the doctrine. A glance indicates that this is no simple matter, as indicated by his several seemingly conflicting statements and competing scholarly interpretations. I will only venture to say that the doctrine is essential to limiting government, if government we must have. (I’m not convinced.) Any principle or taboo that would inhibit the growth of the state and leave room for individual freedom is to be desired. As Thomas Jefferson wrote, “The natural progress of things is for liberty to yeild [sic], and government to gain ground.” Thus, he also said, the proper attitude toward government is not confidence but vigilance.

At any rate, it doesn’t really matter how committed Montesquieu was to the doctrine. We can make up our own minds. Quoting Montesquieu on behalf of the doctrine should be useful to liberty-minded people. So let’s do it. The passage is from Chapter VI: Of the Constitution of England. Montesquieu wrote:

The political liberty of the subject is a tranquillity of mind arising from the opinion each person has of his safety. In order to have this liberty, it is requisite the government be so constituted as one man need not be afraid of another.

When the legislative and executive powers are united in the same person, or in the same body of magistrates, there can be no liberty; because apprehensions may arise, lest the same monarch or senate should enact tyrannical laws, to execute them in a tyrannical manner.

Again, there is no liberty if the judiciary power be not separated from the legislative and executive. Were it joined with the legislative, the life and liberty of the subject would be exposed to arbitrary controul; for the judge would be then the legislator. Were it joined to the executive power, the judge might behave with violence and oppression.

There would be an end of every thing, were the same man, or the same body, whether of the nobles or of the people, to exercise those three powers, that of enacting laws, that of executing the public resolutions, and of trying the causes of individuals….

Here, then, is the fundamental constitution of the government we are treating of. The legislative body being composed of two parts, they check one another by the mutual privilege of rejecting. They are both restrained by the executive power, as the executive is by the legislative.

To say the least, this is out of step with today’s chief executive, who presses for autocratic power on virtually every front—from redesigning the White House to “emergency” tariffs to detention and deportation without due process to extrajudicial murder on the high seas and in Somalia. His attempt to control speech and generally dictate the terms of our economic relations betrays a failure to appreciate an even more important separation: of the government and our private lives. He didn’t begin the erosion of those separations; that happened long ago. But he certainly has accelerated it.

If political power must exist, it must be contained, and the way to do that is dispersion among branches and levels. To be sure, the separation of powers and the related checks and balances could impede efforts to roll back power, but preventing new expansions of power seems the higher priority now. No one said that establishing full liberty would be easy.

Mr. Trump no doubt regards the separation-of-powers doctrine as a mere petty annoyance, something his enemies only recently concocted to thwart his grand ambition to be adored a thousand years from now. With barely any exception, the legislative branch of the central government has had no stomach to challenge him. Fortunately, some courts have pushed back. How The Maestro takes a major setback at the Supreme Court, if one should occur, will be instructive.