首楞嚴義疏注經 1.397

1.397

不兼根故，名為非知。不兼境故，名非不知。二義既非，將何以表心之體性。體性不有，中位自無。

Because it does not combine the faculty, it is called 'neither knowing'; because it does not combine the object, it is called 'nor not-knowing'. Both senses being negated, by what could the substantial nature of the mind be indicated? If a substantial nature does not exist, the intermediate position naturally does not exist.