 Pankenier argues that the supreme Di was identified with the celestial pole, an idea familiar in later stages of Chinese religion, linking with the "Tàiyī" 太一 ("Great One") fully documented as early as the 4th century BCE.The interpretation of Shangdi as the celestial pole, Taiyi and as Ku the progenitor of the Shang is not contradictory.Feng Shi argues that Ku and Di are indeed identical.