Excerpts from The Secret Meanings of the Heart Sutra
Venerable Xiao Pingshi
The hidden meaning of “Bodhisattva Guanzizai” is as follows. The True Mind and the illusory minds jointly work together. This indicates that the eight consciousnesses (the minds) of beings within the desire realm work together synergistically. One who has realized the True Mind and can directly observe and comprehend that it inherently and independently exists by itself and coexists with illusory minds is referred to as a “Bodhisattva Guanzizai.”
Let me ask, then, is there an observer in the state described by the term Guanzizai? Is there an object to be observed? The answer to both is “Yes!” If there is no mind that can observe, how can one “observe and comprehend that the True Mind inherently and independently self-exists”?
However, the observing mind is not self-existent. Instead, we should employ the observing mind to observe another mind that inherently exists by itself. A bodhisattva who has located this mind that has existed primordially and is able to directly observe and comprehend in the aforementioned way is a “Bodhisattva Guanzizai.”
The Secret Meaning of the Heart Sutra, p. 222