Sometime around 1912, painting changed. Artists from Moscow to Westport, by way of Munich and Paris, began making abstract works. “Observers spoke of the exhilaration and terror of leaping into unknown territory,” Leah Dickerman writes in the catalog for “Inventing Abstraction, 1910–1925: How a Radical Idea Changed Modern Art,” the monumental exhibition she has curated at the Museum of Modern Art in New York City, on view through April 15. This saut dans le vide, she notes, was “accompanied by a shower of celebratory manifestos, lectures, and criticism, a flood of words flung forth perhaps in compensation for their makers’ worry about how the meaning of these pictures might be established.” It also brought a deluge of labels: “pure painting,” “nonobjective painting” and many more, with “abstraction” being merely the…