Callahan never considered himself to be a "mystic" painter. In writings and interviews he explained that he wasn't interested in symbolism; rather, he saw his work as being firmly rooted in nature and art history - as it plainly was through the early part of his career. By the early 1960s, however, his style had become much more complex - and seemingly rife with symbolism. "He liked muscle-bound grandeur," wrote arts journalist Regina Hackett, "but released the figures who displayed it from the confines of gravity. Full of light, many hover on the edge of floating away." Over time, figurative elements - men, horses, trees, insects - disappeared from his work, in favor of pure abstraction, but still, said Callahan, "It is nature, with its unlimited varied form, structure, and color that constitutes the vital living force from which art must basically stem."