In my earlier editorial “5,000 millionaires,” I wrote that Charlie Kirk brought diverse perspectives and important debates to college campuses. What I failed to mention was the courage that required. It takes courage to walk into rooms where almost everyone disagrees with you, and some outright hate you for your views. It takes even more courage to keep showing up as political violence has grown in America, with too many campuses turning into flashpoints where conservative speakers have been shouted down, harassed or worse. Mr. Kirk kept coming anyway. And now, too little, too late, I acknowledge that courage directly.

In that same piece, I also debated some of his points. I disagreed with certain conclusions about education and opportunity, and I wrote as much. But I believe Mr. Kirk would have respected that, because, like me, he sought the cooperative solution in the game theory of free speech. His willingness to face hostile crowds and take questions from all sides showed that disagreement itself was part of the pact. Debating those issues with him in person was a dream of mine. That dream is gone now.

My editorial “Game theory and free speech” offered a way to understand why this cooperative pact matters. In game theory, a grim trigger is a rule: I’ll cooperate as long as you do; the first time you defect, I switch to permanent noncooperation. Applied to politics, the cooperative rule is “we all let each other speak.” The defection is “you don’t get speech,” shouting down, de-platforming, threats or violence. Once someone pulls that grim trigger, the interaction shifts from persuasion to payback, and escalation becomes the “rational” path. Fitting, then, that the language is so stark. A trigger was pulled at Utah Valley University, and with it, the cooperative framework that sustains democracy took another devastating blow.

Mr. Kirk’s assassination is not just a tragedy for his family, friends and followers. It is the kind of disaster that a growing pile of “broken windows” makes more likely. In my last editorial, “Broken windows and broken politics,” I warned that tolerating “milder” forms of political violence and intimidation would erode the norms that keep conflict peaceful. Blocking roads, defacing buildings, open intimidation at rallies — once those behaviors are treated as normal, they raise the likelihood of something worse. Once those things become routine, the only way some unhinged people think they can make an impact is by going further, by pulling the grim trigger and crossing the line into true violence. And now, the worst has happened.

The past decade has seen Americans retreat deeper into partisan corners. Polling makes clear that partisanship is sharper now than at any point in living memory. Instead of sharpening ideas through debate, too many have chosen to sharpen knives against their neighbors. Mr. Kirk’s greatest contribution was to fight against that drift by showing up on campuses in person and inviting political engagement. His videos make it clear: students from all sides showed up to argue. Conservative ones, who often felt abandoned by their institutions and tempted to disengage, came back to debate instead of disappearing into the void of online echo chambers. He pulled people back into the realm of speech.

That’s why this assassination cuts deeper than the loss of one life. Words are not violence. But bullets are. The more we confuse the two, the more we justify actual violence as an acceptable political tool. That road ends in tragedy, again and again.

The only credible way forward is a recommitment to free speech. That means tolerating, even defending, the voices we most dislike, because silencing them is always a short-term victory that breeds long-term decay. It also means rejecting a style of politics that turns immutable characteristics into battle lines. Once race, religion, gender or geography become the foundation of our conflicts, speech no longer suffices. Those lines don’t move. And when politics is built on immovable lines, violence is the only escalation left.

Mr. Kirk understood this. He had the bravery to keep walking into rooms where few agreed with him and many despised him, because he knew free speech was the cooperative solution. The best way to honor him now is for our institutions to move decisively toward that same cooperative path.

Gavin Roberts is an associate professor of economics and chair of the economics department at Weber State University. He is a recipient of the Gordon Tullock Prize from the Public Choice Society and regularly shares his research locally, nationally and internationally. This commentary is provided through a partnership with Weber State. The views expressed by the author do not necessarily represent the institutional values or positions of the university.