You’ve seen the pictures. Statues are being pulled down, decapitated and sprayed with graffiti. Confederate symbols and monuments to colonizers are under attack. It’s happening in Richmond. It’s happening in Boston. It’s even happening in Britain.

These acts are all forms of iconoclasm. They may be destructive in nature, but they’re full of meaning. They are, most obviously, acts of protest, forms of political speech. What they communicate is simply: “Enough! Enough with valorizing people who were responsible for slavery, racism, and murder. Enough with ennobling what is morally repugnant.”

To this blurt of righteous anger, the iconoclasts add nuance: “To celebrate such people, to cast them in bronze, to put them on a stone pedestal in the most prominent parts of town, to surround them with flower beds, even just to tolerate their presence, is to rub salt into a wound that has no chance of healing for as long as they are there. If you won’t take them down, we will.”

This is powerful. And it prods me to try to compare the current moment to history’s other periods of iconoclasm. There have been plenty. In fact, wherever there is power, there are images of power, and wherever there are images of power, there is iconoclasm.

Art historians and theologians tend to focus on the religious roots of iconoclasm. (It is, strictly defined, a religious phenomenon.) The monotheistic religions — Judaism, Christianity and Islam — all have rules against worshiping images that act as stand-ins for God and thereby risk being mistaken for divinities themselves. (In the Old Testament, the relevant commandments are Nos. 1 and 2; in Islam, it is the Shahada, the first of the faith’s Five Pillars.)

A cult of icons developed in 8th-century Byzantium, where iconoclasm originated. Alternating emperors issued edicts banning and then permitting them. Interestingly, whenever a more permissive emperor took power, people were astonished to see the number of icons, thought destroyed, that suddenly emerged from hiding.

A notorious outbreak of iconoclasm occurred in the 16th century, during the Protestant Reformation. In England, monasteries were stripped of their contents, and holy images from across the country were shipped to London, where Thomas Cromwell, the king’s chief minister, staged public burnings.

Seven more years of destruction ensued under the boy-king, Edward VI. Orders were issued to “take away, utterly extinct and destroy all shrines . . . pictures, paintings, and all monuments of feigned miracles, pilgrimages, idolatry, and superstition; so that there remain no memory of the same.”

Put that way, it sounds quite exciting. But what was the motive?

The theological debate pales, I think, beside the political and psychological imperative. The key phrase comes at the end of the edict: All this should be destroyed “so that there remain no memory of the same.”

To take down offensive statues and images is to remove what you perceive as a moral stain. But it is also to destroy an aid to historical memory.

That is by no means always a bad thing. It can be exhausting and demoralizing always to have to remember. To be actively reminded against your will — as happens with public monuments — can be especially infuriating.

If, as an African American, you are out with your kids or walking to work, why should you have to pass by a giant statue of Robert E. Lee — a man who led the fight to maintain the enslavement of your people? Why should the city — your city, where you pay taxes — be planting flower beds around such a statue?

Take it down.

Every community, every nation, builds its identity on a strange weave of shared remembering and shared forgetting. Disagreements about what should be remembered and what forgotten can be productive and dynamic. But sometimes — like now — that dynamism spills over into anger and conflict.

History is contradictory. It is full of inspiring moments, inspiring people and inspiring institutions. These stories are important to tell. But we must be honest. History is also what James Joyce’s character Stephen Dedalus called “a nightmare from which I am trying to awake.” It is a long concatenation of what are often called “moral failures” but are more usefully seen as immoral successes: victories of greed, exploitation and the brutal exercise of power. The aftereffects of these traumatic “successes” continue to crash over us.

Which is why every nation struggles with shame.

Some things are so shameful that remembering them is not always the salve an enlightened consciousness would like it to be. James Fenton, in his poem “A German Requiem,” caught the feeling of shame in The Post-World War II German psyche when he wrote: “How comforting it is, once or twice a year,/ To get together and forget the old times.”

Almost a century after the rampage inspired by Cromwell, a second wave of iconoclasm swept through England. Even as it seeded what grew into the United States of America, this second, Puritan wave led to destruction far worse than during the Reformation. All holy days, including Christmas, were banned. Shakespeare’s Globe Theatre was pulled down. The king was executed.

Commissioners were appointed to “demolish and remove out of churches and chapels all images, altars . . . crucifixes, superstitious pictures, and monuments and relics of idolatry.” England’s great cathedrals were ransacked, burned, transformed into military barracks or marketplaces.

All this transcended theology. It was political. It was an attempt to dismember the entire visual infrastructure of Charles’s monarchy. “As a result of this holocaust,” wrote the historian Roy Strong, “little remains today to evoke the magnificence of Tudor and Stuart regal splendor.”

Just as it is doubtful that 17th-century Puritans would have lamented the loss of anything that evoked “the magnificence of Tudor and Stuart regal splendor,” it is hard for those who loathe the institution of slavery to lament the loss of statues, or plantations, or movies or any other material legacy that evoke the so-called splendor of the antebellum South.

And yet it’s also true that sometimes, for some people, the passage of time alters their perspective, and makes them more eager to remember — both the good and the bad.