In the Tate Modern’s major Philip Guston retrospective, the artist is quoted ruminating on his relationship to paint and processed meats. “It took me a few years to get the feeling of red, and particularly cad red medium, which I happen to love,” he says. “I like pastrami. I just like it. I couldn’t tell you why.” This non-sequitur is darkly funny to anyone familiar with Guston’s most famous paintings from the 1960s and 70s, cartoonish scenarios of white-hooded figures plotting, planning, and chilling in nondescript cityscapes and domestic spaces. These images are perturbing. For the most part, they are also completed in an instantly recognisable and undeniably pastrami-like palette dominated by reds and smeary, white-streaked pinks. In Guston’s best work, moral self-searching is inextricable from the iconography of mundanity. The quote is a sliver of what is so fascinating about his entire oeuvre: an intense interest in the sensual materiality of paint—the feeling of cadmium red pigment—combined with a free association with seemingly benign items of modern life—sliced beef—and a nod to the importance of intuition. He knows what he likes, what he is drawn to. He couldn’t tell you why. The Tate exhibition is a wallop of a retrospective: a once-in-a-generation show that deepens our understanding of twentieth-century painting and politics by bringing together a lifetime’s work by one extraordinary artist.