四明十義書 1.154

1.154

又如上人所解，須是久修止觀之人方能託事修觀。今何故正觀之心却在色心門修習？內外一門正論觀法，今來翻成旁論觀法。何者？以將色心門中正觀，旁歷外境諸法故。內境觀一科既齊任運泯合之句，乃只是外觀成相也。

Furthermore, according to your reverence's explanation, only someone who has long cultivated calming and contemplation can entrust to phenomena and cultivate contemplation. Why now is the mind of direct contemplation instead cultivated in the Gate of Matter and Mind? The single gate of Internal and External directly discusses the contemplation method, yet now it turns out to discuss the contemplation method collaterally. Why? Because you take the direct contemplation in the Gate of Matter and Mind and collaterally range across all external objective dharmas. Since the rubric of the internal object and contemplation is equated with the phrase 'spontaneously fuse in unison', it is merely the characteristic of the external contemplation being accomplished.