I toured Auschwitz in Poland on the same day a man drove a truck through a crowd of people in the south of France. More than 80 people were killed in France. Millions were killed at Auschwitz. This world breaks our hearts.

We might blame religion or ideology for all of this slaughter, but beneath the ideology is a human disease. Cruelty is common. So is indifference. The cure is compassion and responsibility.

At Auschwitz, mechanized mass murder became routine. Victims arrived on trains. They were systematically exterminated, desecrated and incinerated. The process was cold, systematic and industrial.

Who could do such things? And why do they continue to happen?

Primo Levi, an Auschwitz survivor, suggested that Auschwitz remains with us. He described the disease of Auschwitz as “the denial of human solidarity, obtuse or cynical indifference to the suffering of others, the abdication of the intellect and the moral sense in the face of authority, and at the root of it all, a tide of cowardice, an abysmal cowardice, masked as warrior virtue.”

Hannah Arendt, a German Jewish philosopher, called our attention to “the banality of evil.” She thought that great evil resulted from mediocre people acting thoughtlessly. She described Adolph Eichmann, who implemented the “Final Solution,” not as a monster but as a clown.

Cruel deeds and evil ideologies are common, as is thoughtless buffoonery. The challenge is to remain appalled in a world awash in murder and mayhem. The worst thing would be to view evil and stupidity as normal, natural and unavoidable. The worst thing would be to return evil for evil with an indifferent shrug that fails to be revolted by the horrors of the world.

That is why we need hope.

Philosopher George Santayana once said, “Those who cannot remember the past are condemned to repeat it.” This phrase is quoted at the beginning of the tour of Auschwitz.

The quote is taken from a much larger book in which Santayana argues that human nature is not fixed. New species evolve. New ideas emerge. Improved social structures and moral ideals are imaginable. Santayana concluded with a hopeful thought, “evils are transitory and better times may come.”

But for better times to come, we must continue to be outraged by cruelty and thoughtlessness. We must continually acknowledge the depth of human depravity if we are to avoid it. And we must recognize that we can and do evolve.

Memorials to the victims of the Holocaust are found across Germany, including in the heart of Berlin. Last month, the German parliament voted to recognize the Armenian genocideand Germany’s complicity with the Ottoman Empire during the First World War. This acknowledgement of the Armenian genocide is part of an ongoing project that takes responsibility for evil and says, “Never again.”

The German parliament includes a number of ethnically Turkish politicians, who voted in support of the Armenian genocide resolution. Germany’s multicultural parliament is quite different from the racially homogeneous vision of the Third Reich. Evolution occurs.

But things also stay the same. Turkey condemned the Armenian genocide resolution. It called the Turkish-German politicians who voted in favor of the resolution traitors. It recalled its ambassador from Berlin. There were death threats.

And so it goes. And so it will go, unless we stand together against violence, intolerance and stupidity.

The Auschwitz memorial celebrates one story of moral courage. A Polish priest, Maximilian Kolbe, was sent to Auschwitz. In July of 1941, the commandant sentenced 10 prisoners to a miserable death by starvation. Father Kolbe volunteered to die in place of one of these men. He survived 10 days of starvation and was executed by lethal injection.

Father Kolbe was eventually canonized. A phrase attributed to him provides a warning and an inspiration: “The most deadly poison of our times is indifference.”

In a bleeding world, indifference is a defense mechanism. There is often too much stupid cruelty to bear, so we turn away. It is easy to lose faith in the future. But revulsion in the face of evil is a sign of our humanity. We ought to be apalled.

And then we ought to work to make this a world that doesn’t break our hearts.