A General Account of Stems and Branches (Gan Zhi Zong Lun)

Above and below must agree

The chapter's central demand is coherence: what heaven (the stems) brings should be carried by earth (the branches), and vice versa. When the whole upper layer is one qi and the lower layer cannot hold it, or when the branches form a solid triad and the stems cannot accommodate it, the chart is out of joint no matter how good the individual pieces look. Practically: read the four pillars as two layers in dialogue, and treat a stem with no root and a root with no stem as the two basic structural faults.