As a young man in the 1950s, he fled communist Bulgaria, then part of the totalitarian Soviet imperium. When the Berlin Wall went up in 1961, he made a wall of oil barrels on the Rue Visconti in Paris. From 1964 to 1967, he lived as an illegal immigrant in New York with his late wife Jeanne-Claude, before getting a green card and becoming a citizen in 1973. By the time America opened its arms to him, he had been stateless for 17 years. Freedom meant something. The United States was more than a country; it was an idea.

His great works — the 7,503 “Gates” that threaded a tapestry of deep saffron across Central Park in 2005, the wrapping of the Reichstag in polypropylene, the 3,100 umbrellas deployed along inland valleys in Japan and California — have all been about freedom. Within weeks they were dismantled. Nobody could own them. Possession and freedom make uneasy bedfellows. The fabric he used expressed something nomadic, his own life. The works awoke in people a sense of collective wonderment. Huge crowds came. These creations seemed dreamed, yet they existed, and then were gone. They were insubstantial yet immense. Their unlikely beauty was liberating.

For more than two decades, Christo has labored to create a work called “Over the River” in Colorado — a canopy of silvery fabric that was to have been suspended for two weeks over 42 miles of the Arkansas River, a flowing, billowing liquid mirror. But now, after spending some $15 million, he has walked away in perhaps the biggest single act of protest by an artist against Donald Trump. Much of the land is federally owned. As Christo explained to my colleague Randy Kennedy earlier this year, “The federal government is our landlord. They own the land. I can’t do a project that benefits this landlord.”

In Doha, Christo, who is 81, refused to sit down. Defiance is part of him. To live freely is an immense act of will. For an hour he spoke with irrepressible vitality. Eat little, he counseled, in order to channel energy (in his case yogurt with garlic for breakfast, then nothing until dinner). Decide what you want — that is the most difficult part — and then apply yourself without compromise to that end.

Last year he made another work involving water, called “The Floating Piers,” at Lake Iseo in northern Italy. On top of 220,000 interlocking polyethylene cubes, Christo installed a glowing unfenced walkway connecting an island in the lake with the shore. Over a couple of weeks about 1.2 million visitors came. They wanted to walk on water. It’s possible to walk on water. In times of oppression freedom is also a fierce act of the imagination.