Unlike Duchamp, whose work can be difficult and arcane, Baldessari is a conceptualist with a common touch. Or rather a common non-touch. His work is accessible, unpretentious and occasionally glib, and it has proved irritating to some of his more theoretically inclined contemporaries. In 1969, in the essay “Art After Philosophy,” Joseph Kosuth, a fellow devotee of text-based art, derided Baldessari’s artworks as so many conceptual “cartoons” that are “not really relevant to this discussion.”

But then Baldessari was never an artist’s artist so much as a graduate student’s artist. His openness and tolerant irreverence made him inordinately popular as a teacher, and his reputation soared when he arrived at CalArts, a no-grades-no-requirements school, where he declined to teach painting and instead named his course, rather provocatively, “Post-Studio Art.” The implication was that the atelier was a thing of the past and students, instead of aspiring to Promethean creative heights, could be more contemporary as recyclers of found photographs and other appropriated material.

Among his many memorable students who left California and carried his influence to New York are David Salle, James Welling, Barbara Bloom and Edward Henderson. Asked about his teacher’s style, Mr. Henderson recalled, in a reverent tone, “Whatever he said meant 20 things.” Many of his students kept up with him after they left school, and he amiably answered their phone calls and mail. Mr. Henderson pulled out an old postcard from Baldessari, circa 1983. On the front side, it shows an unironically cute scene at the Cincinnati Zoo: four white tiger cubs at play.