One of the most arresting works in “America Is Hard to See,” the inaugural exhibition of selections from the permanent collection at the Whitney Museum of Art’s new Renzo Piano building, was a large red canvas covered with repetitive, staccato brushmarks. The picture was striking for its freshness and visual pulse. Notes of clear blue flickered at unpredictable intervals against the disjunctive, vividly colored field, as if escaping from beneath, while glimpses of an apparently continuous darker hue, underlying the glowing, mosaic-like expanse of red, made the web of rhythmic strokes seem to float, contradicting the obvious fact of their being records of the placement of pigment on a flat surface. The painting, fairly straightforward at first acquaintance, was made increasingly complex by the tension between the exuberant play of color, which seemed completely intuitive, and the disciplined facture, which suggested a slow, deliberate process of construction—one stroke of a certain size and then another and then another. The longer one looked, the more unpredictable the picture became. Those vertical rows of apparently regular, repeated brushmarks revealed themselves as slightly off-kilter, and slightly irregular, creating a compelling visual instability. Surrounded by more familiar works by often celebrated makers of abstract art, this forthright, forceful canvas more than held its own. The work was, of course, Mars Dust(1972), by the distinguished African-American abstract painter Alma Thomas (1891–1978), a canvas acquired by the Whitney the year that it was painted, when the exhibition “Alma W. Thomas” was seen there—the first