Over the weekend, we saw the best of America: Americans helping Americans in Houston. Race, creed, color — none of it mattered. Americans were in need, and other Americans moved to help them.

Meanwhile, in Berkeley, we saw the worst of America: Americans, garbed in black, helmeted, wearing bandannas over their faces, assaulting peaceful protesters merely there to exercise their free speech rights. We saw the police stand down. We saw assaults in the streets.

So, what’s the difference between Americans in Houston and Americans in Berkeley?

The existential threat.

Human beings unify in the face of an existential threat. It’s why members of the military become brothers; it’s why the West unified in opposition to Communism; it’s why Americans unified after 9/11.

In Houston, the existential threat is nature. And Americans who wouldn’t share a meal are now sharing speedboats, attempting to help each other survive her wrath. Survival is the top priority; death is the ultimate enemy.

But remove that existential threat, and people look for a new existential threat. That’s what we’re seeing in Berkeley: Americans defining one another as an existential threat. Antifa defines the “system” as an existential threat — a wellspring of racism, bigotry, and economic injustice. And they define anyone who disagrees with them as a “fascist” worthy of violence. This is horse manure, but it’s their justification for their violence. Similarly, as Charlottesville shows, the white supremacist alt-right finds itself a different existential threat: non-white people whom they believe are inherently unable to assimilate to Western civilization. Their argument is absolute racist garbage, but because they believe it, that means that all those who don’t become their “cuck” enemies.

To define our existential threat, in other words, we must define ourselves. And right now, we’re breaking down along tribal lines, along class lines. We’re not breaking down along the lines of principles: non-violence in politics; free speech; rights inherent in human individuals free of government. The founding vision has been undermined, and so we search out abroad in favor of new dragons to slay. Meanwhile, the real dragons grow at home, in the form of those who see the founding vision as the problem.

If we want more Americans like those in Houston and fewer like those in Berkeley, we’d do well to remember we share a republic — and we share more in common than the danger of death. We share a common ideal. And if we don’t, we become our own worst enemies.