THIS MORNING AS I was reading A.C. Grayling, who was studiously not getting to the point about the morality of carpet-bombing Germany during World War II, I made one of those delightful discoveries that reward even the casual study of history and philosophy.

Discussing whether the Allied bombing was done for a just purpose (i.e. not to cause civilian suffering), Grayling goes on a multi-page excursus about the 17th century Dutch philosopher Hugo Grotius. I had seen Grotius’s works referenced before but never really acquainted myself with him. That will change. Grotius, it turns out, is the intellectual father of international law. Because he wrote during the Thirty Years War, he had plenty of fodder for thinking about the rights and wrongs of combat.

One case of which Grotius was aware was the sacking of Magdeburg in 1631. In what we would today call a “clearing operation,” a Catholic army defeated Magdeburg’s Protestant defenders and proceeded to rape, pillage and plunder on a Homerian scale. They then burned the city to the ground, and its ashes wafted for miles around, a useful warning to other Protestants. Incensed by such monstrousness, Grotius spotlighted the fact that the combatants in the Thirty Years War committed the same atrocities as all the “barbarian” armies before them, despite their Christian morals. Once the dogs of war were loosed, Christians of both camps sank to the worst imaginable behavior. And it had always been so, not just in Magdeburg. So Grotius set about writing On the Law of War and Peace, a trilogy that would establish a framework of international law grounded in principles of common human decency. Today international law helps protect civilians around the world, albeit imperfectly.

The fact that Grotius had to reach back to non-Christian sources (the Stoics) to build his legal framework jolted me. The surprise was not that that Stoics surpassed the Church in the scope of their ethics–I was well aware of that–it was that Grotius, by shifting Christian Europe’s whole “discussion” of just war to a secular footing, became a major individual agent of change in European history. He singlehandedly helped Europe turn a corner toward the rule-of-law tradition it enjoys today.

He also did something for me.

Since 2001 I have occasionally comforted myself with two observations about the West’s essential differences from its Islamist adversaries: (1) the Christian West is older and therefore more politically mature than its adolescent cousin in the Islamic Middle East, and related to this, (2) in our realm, religion no longer contends for state power. No doubt religion seeps into our political culture, especially in America, but nowhere in the West does it mount–or even think it can mount–a campaign to rule a nation. Christianity has politely recused itself from public authority. Looking back to Grotius’s time or, say Torquemada Spain, this is a miraculously good development, and one that seems irreversable.

In Grotius I see a writer who helped bring this miraculous change about. It was not just the nameless, faceless tides of history that pulled us insensibly toward a better future; particular people did it, and Grotius was a giant among them. He was, and is, a hero of human decency.