四明十義書 2.103

2.103

所言非謂心獨是理者，蓋上人承上偏約事解於諸法，獨約理體解於心法，致得談理便作觀心。為破此計，故云非謂心獨是理也。作此說者，欲令上人悟解心及諸法皆是即理隨緣之事。佛法生法不同心法。生佛諸法既高既廣，初心為難觀，心法近要易可觀察。故知此難正欲難不用妄心為境。因何酬答不得，故剛然改作不許唯觀心耶？

What was meant by 'it does not mean that the mind alone is principle' was because you, Reverend, following your predecessors, one-sidedly explained all phenomena in terms of phenomena and exclusively explained the mental factor in terms of the principle-essence, with the result that whenever you spoke of principle, you took it to be contemplating the mind. In order to refute this assertion, I said, 'It does not mean that the mind alone is principle.' The reason for speaking thus was that I wished you, Reverend, to realize that both the mind and all phenomena are phenomena that follow conditions while identical to principle. The Buddha-dharma and the sentient-being-dharma are not the same as the mental factor. Since the phenomena of sentient beings and Buddhas are both lofty and vast, they are difficult for beginners to contemplate, whereas the mental factor is proximate and essential, easily observed. Thus we know that this challenge was precisely intended to challenge your failure to use the deluded mind as the object. Why, being unable to respond, did you obstinately twist it into [my] not permitting contemplating solely the mind?