起信論疏筆削記 19.9

19.9

然二門下，三、釋成雙運所以。謂依一心上開二種門，依此二門修於止觀，止觀雙運方得契心，契心方名真止觀也。故天台云：法性寂然名止，寂而常照名觀。此乃以修止觀契性止觀也，雙修之旨豈徒然哉。

From 'However, the two gates...' onward, the third part explains the reason for their dual functioning. That is, relying on the One Mind, two gates are opened; relying on these two gates, one cultivates calmness and insight. Only when calmness and insight function dually can one tally with the Mind, and only when tallying with the Mind is it named true calmness and insight. Therefore, Tiantai stated: 'The quiescence of dharmatā is called calmness; quiescent yet ever illuminating is called insight.' This means tallying with essential calmness and insight by means of cultivating calmness and insight; how could the principle of dual cultivation be in vain?