金剛經纂要刊定記 1.30

1.30

Furthermore, the two clauses mutually explain and complete each other: using the upper clause to explain the lower clause completes the meaning of form being empty; using the lower clause to explain the upper clause completes the meaning of the mind being pure. If form were not empty, the mind would not be pure; if the mind were not pure, form would not be empty. Because the mind is pure, form is empty; because form is empty, the mind is pure. Because the two dharmas of form and mind are inseparable, one should know that only because the mind is pure can it manifest form. Just as only because a mirror is pure can it manifest images, whereas if defiled it cannot. Furthermore, because form is empty, it cannot stain the mind; just as because an image is empty, it cannot defile the mirror, whereas if real, it would defile it. The upper and lower clauses, Dharma and metaphor, are clarified in contrast to each other, recurrently complementing one another; hence it is called mutual explanation.