A couple of weeks before Labor Day, New York City Mayor Bill de Blasio triggered a firestorm by suggesting he might order the removal of Christopher Columbus’ statue from Manhattan’s Columbus Circle.

Americans used to celebrate the courage of Columbus and other explorers who courageously set out into the unknown and began the process of introducing western civilization to this new part of the world.

Today, that triumphalist account no longer suffices. We think now of the extraordinary presumption of sticking a flag in someone else’s land and calling it yours. We think more darkly of how European diseases more than decimated the native peoples of the Americas and how poorly the early explorers — Columbus included — treated the native Americans. And we think most darkly of the stain of the slave trade that followed European contact with what was only to the Europeans a “new world.”

These dark thoughts are not misplaced. Yet, when we think them we also should remember what the world was like when Europeans collided with the natives of North America and why that world no longer exists.

Europeans headed west in the 15th century to what they thought was Asia because they were blocked from going east by the Muslim empires of the time.

In Asia, of course, was China, rich and powerful beyond anything to which the Europeans could aspire. Compared to the Muslims and Chinese, the Europeans were poor, backward and weak.

The Europeans suffered as the weak always do. Terrible plagues from Asia brought by commerce already had killed 100 million Europeans.

Europeans also suffered from slavery. Indeed, for many years Europe’s most valuable export to the Middle East was its own people, sold as slaves by the Vikings. The English word “slave” comes from a word still used to describe some eastern Europeans, “Slav.” In the period from 1530 to 1640, Muslim raiders captured and enslaved an estimated 1 million Europeans.

The Europeans who conquered the Western hemisphere acted as people had always acted, no better or no worse; those they conquered suffered as the weaker always suffer, as the Europeans themselves had suffered.

This is evident if we look at the first European conquest outside Europe. The Europeans began to assert themselves with the 1415 conquest of Ceuta, across the Strait of Gibraltar from Spain. They conquered Ceuta from the Muslims, which was a dreadful thing to do, as it was when successive Muslim rulers took it by force from each other, after the first of them took it from the Berbers, who had seized it from the Byzantines, who had taken it from the Vandals, who had taken it from the Romans, who had taken it from the Carthaginians, who undoubtedly took it from others, now lost to history.

Of course, to say that Europeans acted as others had acted doesn’t justify the awful things Europeans did to each other, and to non-Europeans, in their long history. But it might persuade us to moderate our condemnation of Columbus and to judge him less harshly.

We should remember too that we judge him harshly now because the same power that enabled the Europeans to conquer the world also allowed them to impose their later views of human rights on the world.

Even as the conquest was reaching its zenith in the 19th century, Europeans were bringing to the world the then novel idea that one group of people did not have the right to impose its will on another group.

This revolution in thinking was announced by the Declaration of Independence and its assertion of the self-evident truth of human equality. It was carried further by the British who suppressed the slave trade with their all-powerful navy, commercial might and insistent diplomacy, and led the campaign for the abolition of slavery. It was completed by American insistence after World War I and II that people everywhere have the right to self-determination.

This Columbus Day we need no triumphalism. Instead, let it be a day to ponder the good and evil that humans are capable of and to wonder how we might encourage more of the good.