What religious belief allowed the Zhou dynasty to rule?

The Mandate of Heaven

In the previous period of rule by the Shang dynasty the Mandate of Heaven was proposed as the reason for why a dynasty would rule. The Shang claimed that they had taken control from a previous dynasty the Xia. They believed, because the Xia rulers had become corrupt, that the favor of heaven had fallen upon the Shang to take control. It is debated whether or not the Xia dynasty really existed. By the time the Zhou took over from the Shang, though, the doctrine was firmly established.