As the direct use of sign, analogy is also applied by Chih-i to clarify certain issues. For example, to reveal the meaning of the Substance as the Ultimate Truth and its relationship with the Gist as the cause and effect of Buddhahood, different parts of a house are taken as an analogy:

“As with pillars and roof beams, houses are neither beams nor pillars but empty space inside a house. Pillars and beams analogize Cause and Effect; neither beams nor pillars analogize the Ultimate Truth. The Ultimate Truth is the Substance but not beams and pillars. If a house has no empty space, it cannot contain anything. If Cause and Effect have no Ultimate Truth, they cannot be founded.”

This analogy distinguishes different functions the Substance and the Gist exert. Yet, the significance of both is indispensable. The Substance is what the Gist can be founded upon, and the Gist is what can display the Substance. (Page 116)