肇論新疏 2.105

2.105

此言若聖心有知，宜置無知；若聖心無知，宜置有知；若聖心雙非，更不復說二名。二名既成，互非三義皆為不可。

This says: if the sage mind possesses knowing, one should set aside "without knowing"; if the sage mind is without knowing, one should set aside "possessing knowing"; if the sage mind denies both, one should no longer utter the two names. Since the two names are established, their mutual negation renders all three positions inadmissible.