Ingenuity is a recurring idea in the book. Desperation is indeed the mother of invention. With resources limited and diminishing, Callahan must address difficult problems in novel and creative ways. With rope and silverware he repairs his harpoon gun and seals a tremendous breach. With his space blanket he fashions a kite and water catchment device. He even patches his solar still with the gummy residue harvested from soggy duct tape as navigates using a sextant fashioned from pencils. Callahan's creativity seemingly knows no bounds.