The Four Siddhāntas that are conveyed in the light of the Four Noble Truths in the Tripiṭaka, Common, and Separate Teachings, are relative teachings. The ultimate teaching of the Four Siddhāntas refers to the Perfect Teaching. Chih-i’s explanation of the Four Siddhāntas in terms of relative and ultimate that are related to each of the Four Teachings is as follows:

1. The Buddha employs only the first three Siddhāntas (i.e., Worldly Siddhānta, Siddhānta for Each Person, and Siddhānta of
   Counteraction) to expound the Four Noble Truths that belong to the Tripiṭaka Teaching. Since this teaching concerns analysis and disintegration of dharmas (entities) in perceiving emptiness and is to prepare listeners with lower faculties to be able to eventually receive Mahāyāna Teaching, it is unskillful in terms of the way of perceiving emptiness, and is relative.
2. The Four Siddhāntas the Buddha employs to expound the Four Noble Truths that belong to the Common Teaching are skillful, for the teaching concerns embodying dharmas in perceiving emptiness. That is, dharmas are empty therein. However, truth is dichotomized into the Absolute Truth and the Worldly Truth: the former concerns emptiness, and the latter empirical existence. This teaching of duality is relative.
3. The Four Siddhāntas the Buddha employs to expound the Four Noble Truths that belong to the Separate Teaching are profound, for this doctrine concerns the Middle Way of transcending the truths of emptiness and existence. However, this Middle Way does not identify emptiness with existence, and is still relative.
4. The Four Siddhāntas the Buddha employs to expound the Four Noble Truths that belong to the Perfect Teaching are ultimate and subtle. This is because this doctrine concerns the Middle Way that identifies emptiness with existence. For Chih-i, such a way of perceiving reality as an integrated unity of both emptiness and provisional existence is perfect and is the ultimate teaching of the Buddha. (Vol. 2, Page 43-44)