In 2017, out went all presidential norms

investigations. Or bully the free press. Or speak kindly of white supremacists and credibly accused child molesters. Or use his office for personal gain when everyone can see him doing it or lie when even babies know he’s lying.

He doesn’t threaten nuclear war via Twitter.

A president simply doesn’t do those things. Except that now, evidently, he does. And that’s scary. Politics — and civil society as a whole — rests on a foundation of largely unspoken agreements, a social covenant that defines us in relation to one another, sets forth the duties we owe and the expectations we maintain in deference to the larger us.

There have always been things our leaders did — and refrained from doing — not necessarily because the doing or not doing violated the law, but because it violated tradition, propriety, common sense, ethics, statesmanship, the dignity of high office and some native sense of right and wrong.

All of which were conspicuously absent from the presidency last year.

The result has been anger, coarseness, political destabilization and a trickledown nastiness visible both in anecdotes and in hate crime statistics. Nor is the source any mystery. As white fans jeered at players from a black and Latino high school during a basketball game: “Trump! Trump! Trump!”

Yes, 1919 brought riots, 2001, unspeakable terror. But 2017 was a sustained assault on the ideal of the larger us.

It taught us how fragile is the social covenant, how susceptible to anyone willing to kick over the table, break the silverware and beat his chest.

It taught us how shamefully docile some of us will be in falling in line behind such an individual.

Thankfully, it also taught us that civil society is not something you take for granted.

It’s a choice you make, a thing you have to fight for.

Which will be a fitting mission for 2018 and beyond.