四明十義書 1.146

1.146

又須知事理不二之語。得意之者，隨修一觀必含二義。如修理觀者，雖云但觀理具，須知全修在性，則善修實相觀也。修事觀者，雖觀能造十界之心，須知全性成修，則善修唯識觀也。

Furthermore, one must understand the phrase 'non-duality of phenomena and principle'. For one who grasps its meaning, cultivating either one of the contemplations necessarily contains both meanings. For instance, when cultivating principle contemplation, although it is said that one only contemplates inherent possession in principle, one must know that cultivation is entirely within the nature; this is skilled cultivation of the true characteristic contemplation. When cultivating phenomenal contemplation, although one contemplates the mind capable of creating the ten realms, one must know that nature entirely becomes cultivation; this is skilled cultivation of the consciousness-only contemplation.