Those moments, I fear, might have to include for me the hours after American troops overran Baghdad in April 2003. At the time, I witnessed and shared the wild public rapture at Saddam Hussein’s fall, which gave way almost overnight to grim forebodings about the murderous sectarian chaos that was to ensue, and which continues, with a redoubled vengeance, in Tikrit, Mosul, Ramadi and dozens of other Iraqi cities and towns where the Islamic State has held sway.

My impatience with ideology has carried over in recent years to my encounters with the societies in the West that are my home: to the widespread propensity, as I have sensed it, for people who lack the excuse of brutal duress that is a constant in the totalitarian world to fall sway to the formulaic “isms” of left and right, each of them full of Yeats’s “passionate intensity,” that excuse, and indeed smother, free thinking.

The bankruptcy of the approach that divides the world into camps of left and right was a lesson learned early. An assignment to China in the early 1970s exposed me to the murderous doctrines of Mao Zedong “Thought,” with victims that numbered in the millions; and a posting to Moscow in the early 1980s, 30 years after Stalin’s death, was redolent of the miseries that a perverted form of Marxism-Leninism imposed on Soviet Russia, with its own ghastly toll in the millions.

My five years in South Africa carried their own lessons. The more I saw of the ugliness of apartheid, the more evident it became that the apparatus of right-wing repression — the twisted ideology, the pervasive role of the secret police, the dehumanization of an entire population — was little different from left-wing dictatorships, save in the sheer number of victims.

If ideology was the scourge of the 20th century, so it has continued to be in many of the worst places of the 21st. Perhaps the most murderous of all states in our time is the North Korea of the Kim family, with millions dead from hunger and the deprivations of vast, hidden prison camps. And the beheadings, mass shootings and burnings-alive committed by the Islamic State have their origins in yet another kind of corrupted, extremist thought.

In all of these places, my experience has been that when it suits the ends of power, ideology can be invoked to prove that 2+2 = 5, or 3, or any other number that suits the state, and to demand that all embrace the madness. It is a truly frightening thing to interview a top-ranked nuclear scientist, or a distinguished brain surgeon, or a concert pianist, as I did in China under the sway of Mao, and to hear them, as ideological outcasts, justify with utter conviction the brutalities inflicted on them by their ideology-crazed persecutors — crushed fingers, smashed heads, broken marriages, vilification by their own families.

Elsewhere, the lunacy was of an order that invited a response of laughing mockery, if that were not potentially fatal to the system’s loyalists, or those pretending to be so. In North Korea, while Kim Il-sung was still alive, there was a brand new, high-tech hospital built in his name in Pyongyang, floor after floor laden with tens of millions of dollars in the latest American, Swiss and German equipment, but no patients to be seen. And why not? “As we have explained,” the most senior comrade-physician responded, “the Korean people’s great leader Comrade Kim Il-sung has taken such care for the health of his beloved people that none of his people gets sick.”

Not ever? “No, never,” was the reply.

My catalog of such moments in the grim dictatorships of the world could fill a book, or three. But coming home to the countries of the West, where nobody dies for a moment’s lapse in fealty to a prime minister or a president, it can be depressing beyond words to hear the loyalists of a given political creed — whether of the left or the right — adopt the unyielding certainties common in totalitarian states. Our rights to think and speak freely have been won at great cost, and we abuse them at our peril.