One of the essential, if often unstated, job requirements of an American president is to provide stability, order and predictability in a world that tends toward chaos, disarray and entropy. When our political leaders ignore this — and certainly when they delight in disruption — the consequences can be severe. Stability is easy to take for granted, but impossible to live without.

Projecting clear convictions is important for preventing adversaries from misreading America’s intentions and will. Our allies also depend on our predictability and reassuring steadiness. Their actions in trade and economics, in alliances with other nations and in the military sphere are often influenced by how much they believe they can rely on American support.

Order and stability in the executive branch are also linked to the health of our system of government. Chaos in the West Wing can be crippling, as White House aides — in a constant state of uncertainty, distrustful of colleagues, fearful that they might be excoriated or fired — find it nearly impossible to do their jobs. This emanates throughout the entire federal government. Devoid of steadfast leadership, executive agencies easily become dysfunctional themselves.

Worse yet, if key pillars of our system, like our intelligence and law enforcement agencies, are denigrated by the president, they can be destabilized, and Americans’ trust in them can be undermined. Without a reliable chief executive, Congress, an inherently unruly institution, will also find it difficult to do its job, since our constitutional system relies on its various branches to constantly engage with one another in governing.

But that’s hardly the whole of it. Particularly in this social media era, a president who thrives on disruption and chaos is impossible to escape. Every shocking statement and act is given intense coverage. As a result, the president is omnipresent, the subject of endless coast-to-coast conversations among family and friends, never far from our thoughts. As Andrew Sullivan has observed, “A free society means being free of those who rule over you — to do the things you care about, your passions, your pastimes, your loves — to exult in that blessed space where politics doesn’t intervene.”

A presidency characterized by pandemonium invades and infects that space, leaving people unsettled and on edge. And this, in turn, leads to greater polarization, to feelings of alienation and anger, to unrest and even to violence.

A spirit of instability in government will cause Americans to lose confidence in our public institutions. When citizens lose that basic faith in their government, it leads to corrosive cynicism and the acceptance of conspiracy theories. Movements and individuals once considered fringe become mainstream, while previously responsible figures decamp to the fever swamps. One result is that the informal and unwritten rules of political and human interaction, which are at the core of civilization, are undone. There is such a thing as democratic etiquette; when it is lost, the common assumptions that allow for compromise and progress erode.

In short, chaotic leadership can inflict real trauma on political and civic culture.

All of which brings us to Donald Trump, arguably the most disruptive and transgressive president in American history. He thrives on creating turbulence in every conceivable sphere. The blast radius of his tumultuous acts and chaotic temperament is vast.
Mr. Trump acts as if order is easy to achieve and needs to be overturned while disruption and disorder are what we need. But the opposite is true. “Rage and frenzy will pull down more in half an hour,” Edmund Burke wrote, “than prudence, deliberation and foresight can build up in a hundred years.”

Mr. Trump and his supporters don’t seem to agree, or don’t seem to care. And here’s the truly worrisome thing: The disruption is only going to increase, both because he’s facing criticism that seems to trigger him psychologically and because his theory of management involves the cultivation of chaos. He has shown throughout his life a defiant refusal to be disciplined. His disordered personality thrives on mayhem and upheaval, on vicious personal attacks and ceaseless conflict. As we’re seeing, his malignant character is emboldening some, while it’s causing others — the Republican leadership comes to mind — to briefly speak out (at best) before returning to silence and acquiescence. The effect on the rest of us? We cannot help losing our capacity to be shocked and alarmed.

We have as president the closest thing to a nihilist in our history — a man who believes in little or nothing, who has the impulse to burn down rather than to build up. When the president eventually faces a genuine crisis, his ignorance and inflammatory instincts will make everything worse.

Republican voters and politicians rallied around Mr. Trump in 2016, believing he was anti-establishment when in fact he was anti-order. He turns out to be an institutional arsonist. It is an irony of American history that the Republican Party, which has historically valued order and institutions, has become the conduit of chaos.

Peter Wehner, a senior fellow at the Ethics and Public Policy Center, served in the previous three Republican administrations and is a contributing opinion writer.