When Donald Trump is sworn in as president on Friday, the United States will embark on a new and very uncertain era.

Trump campaigned as a rebuke to the era of politics that preceded him. He questioned the three pillars of the post-Cold War era: trade liberalization, mass immigration, and political integration. His very personality rebuffs the era that preceded him. Previous presidents rewarded cool-headed men and women, surrounded by a phalanx of policy experts and consultants, who kept the message "disciplined." Trump is a hothead who says what he feels, and he'll feel another way tomorrow.

So as we prepare for the Trump presidency, it's appropriate to take stock of the hopes and fears for the new era. Today, I'll start with my fears.

My first fear is actually that Trump could be a kind of non-president. That he will settle in as a hyperactive head of state, running out to get more headlines and draw up controversy and fight with the press, while leaving the Republican Party and all of domestic policy entirely in the hands of Paul Ryan and Mike Pence. This is the danger of conservatives getting too much of what they want. Instead of a nationalist makeover that puts the power of the government on the side of its citizens and a wall on the border, we get more devotion to the abstract markets, with Trump grinning before the camera.

Some are worried about Trump's personal corruption. I'm not one of them. The corroding financial self-interest of Trump may be epic, but it's not particularly dangerous in and of itself. The political era that preceded him was one in which politicians found respectable and legal ways to monetize their time spent in office, sometimes rather nakedly tailoring their legislative careers to become corporate lobbyists or stars in the world of foundations. The danger here is that Trump's more direct self-dealing will further erode trust in American government.

But the biggest danger of the Trump era is the one that sounds most hysterical to bring up: the danger of sliding into nuclear conflict.

One of the few virtues of the political class that Trump has displaced was its terror of nuclear weapons and its recognition that American power and prosperity rested on husbanding, not exercising, this power. Along with this terror, there was an elaborate form of politesse when it came to talking about nukes.

Trump speaks about nuclear weapons in a way that seems flip and reckless. He has been extremely consistent about his plan to improve relations with America's nuclear-armed rival Russia. But he may find that nations and their leaders don't behave in the way he expects. They may be locked into long-term strategic goals and not see the need to make new impressive sounding "deals" with Trump. Even before taking office, Russia is rebuffing Trump's plan to use the leverage of Obama-era sanctions on Russia to obtain a nuclear arms reduction deal.

Trump's sometimes confusing public statements about the NATO alliance also make nuclear conflict more likely because they create uncertainty in the capitals of America's allies and in Moscow about how the United States will respond to Russia's ambiguous actions along the border. At what point does Putin attempt to take advantage by offending Trump's sense of national pride or sense of manhood? And by that time, what options will Trump have for a response, besides the big one?

Trump's nuclear danger doesn't end with NATO, however. Trump inherits U.S. involvement in a half-dozen intractable conflicts across the Islamic world. And in one of them, in Syria, Russia has expressed a willingness to escalate.

Even before 9/11 a pattern was established for American involvement in the Middle East. When the U.S. intervenes in an Islamic nation there are three results. First, the nation is tipped into chaos in which Islamic terrorists thrive (Libya, the Sunni Triangle, Syria). Second, American troops try to prevent that chaos by remaining in that country seemingly forever, surging and partly withdrawing according to public opinion (Iraq, Afghanistan). Third, American troops withdraw in humiliation after the confusion and body count becomes too much (Lebanon, Somalia).

In the context of half a dozen conflicts that promise long-term and costly management, "why have nukes unless you use them?" is truly frightening.

Lastly, Trump also takes office at precisely the moment when the very last policy advisers who personally remember the awful costs of great power conflict are dying. It was precisely these men who kept the Cold War from getting hot. Do I think the risk of nuclear conflict is particularly high? No. But throughout the Trump era it will be appreciably higher than it has been since 1991. Families, not just policymakers and journalists, should be discussing how to handle it.

But the most immediate thing to be on guard for in the new era is the way Trump inspires both supporters and opponents to abandon their moral, ethical, and professional standards and give in to their unchecked instincts to acquire power and humiliate or denigrate their perceived enemies, usually their fellow countrymen. Trump's political success can be partly explained by the way in which America's culture war has a logic of escalation. Trump's presidency may see a quickening of tempo.

We are already tempted to hate and fear each other and think the worst of each other, especially as we contemplate our country through backlit screens that draw us to them by stimulating our most basic fight-or-flight instincts. The virtues of sobriety and liberality will be denigrated as liabilities by both sides in the Trump era. Expect them to become rarer and more valuable, especially when their value seems less obvious.

Keep your heads on a swivel.

This is the first installment in a two-part series. Read the second article here.