From 1938 to 1942 Pollock worked for the WPA Federal Art Project. During this time Pollock was trying to deal with his established alcoholism; from 1938 through 1941 he underwent Jungian psychotherapy with Dr. Joseph Henderson and later with Dr. Violet Staub de Laszlo in 1941–42. Henderson engaged him through his art, encouraging Pollock to make drawings. Jungian concepts and archetypes were expressed in his paintings. Some historians[who?] have hypothesized that Pollock might have had bipolar disorder. Pollock signed a gallery contract with Peggy Guggenheim in July 1943. He received the commission to create the 8-by-20-foot (2. 4 by 6. 1 m) Mural (1943) for the entry to her new townhouse. At the suggestion of her friend and advisor Marcel Duchamp, Pollock painted the work on canvas, rather than the wall, so that it would be portable. After seeing the big mural, the art critic Clement Greenberg wrote: "I took one look at it and I thought, 'Now that's great art,' and I knew Jackson was the greatest painter this country had produced. " The catalog introducing his first exhibition described Pollock's talent as ". . . volcanic. It has fire. It is unpredictable. It is undisciplined. It spills out of itself in a mineral prodigality, not yet crystallized. "