仁王般若經疏 1.116

1.116

問：若廣說諸法無量，空隨諸法亦應無量。略說應一空，所謂一切法空。今何以但說十八空？答：若略說即事不周，若廣說即事繁。如服藥少則病不除，多則更增其患。空亦如是，若說一空則不能破種種邪見及諸煩惱，若隨種種邪見說空則過多。今說十八空正得其中，今辨十二亦如是。

Question: If one extensively explains, dharmas are limitless, and emptiness, following dharmas, should also be limitless. If explained briefly, there should be one emptiness, namely the emptiness of all dharmas. Why are only eighteen emptinesses taught now? Answer: If explained briefly, the matter is not comprehensive; if explained extensively, the matter is burdensome. It is like taking medicine: if too little, the illness is not eliminated; if too much, it adds to the affliction. Emptiness is also like this: if one teaches a single emptiness, it cannot shatter the various wrong views and defilements; if one teaches emptiness according to the various wrong views, it would be excessive. Now teaching eighteen emptinesses hits the exact middle; discerning twelve now is also like this.