In the new film “Captain Fantastic,” Viggo Mortensen plays Ben, an off-the-grid patriarch raising his six children to be intellectuals and survivalists in equal measure — “philosopher kings” as adept at discussing Marxist theory and speaking Esperanto as they are at hunting game. “The kids have to express some pretty mature ideas and concepts,” Mortensen says. “They have to verbalize things that would be difficult even for an adult actor to sound convincing or knowledgeable about. That takes time, a real effort to get the right casting down and to work with them.”

Before shooting began, the film’s director, Matt Ross, provided Mortensen with a reading list to help him understand his character. As it turned out, however, Mortensen was already familiar with everything on it except for, he says, “a couple very specialized books about Olympic athlete training.” Mortensen, like his character, has spent much of his life split between the outdoors and intellectual pursuits, and he came to set prepared. “I arrived in Washington with a pickup truck full of stuff, including many boxes of books,” he says. “I don’t think he knew that I had lived in the Northwest. I don’t think he knew that I knew about gardening.”

Mortensen, himself, owns a publishing house, Perceval Press, on whose home page he often posts his own reading recommendations. “More often than not,” he says, “it’s something that I happen to agree with, think is of value, and is probably more liberal-minded and so forth.” (During our conversation, Mortensen draws a parallel between the isolationism of his character’s family and the recent Brexit vote: “You are giving up something that you can only get from interacting with others, collaborating in terms of a global community or a regional community,” he says.) Below, Mortensen elaborates on how some of Ross’s reading suggestions — from texts on animal tracking to atheist manifestoes — informed his character.

Image Viggo Mortensen as Ben in “Captain Fantastic.” Credit... Cathy Kanavy/Bleecker Street

“Primitive Wilderness Living and Survival Skills,” by John McPherson

“I like going out in the woods and camping. For a time, I lived in a house in the middle of the forest. I was raised doing those sorts of things by my dad. When I was little, we’d go camping a lot — he taught me to fish and to hunt. Outdoor activities, outdoor life — I’m just curious about it, and the names of plants, what plants you can use, what plants are poisonous.”