Here, Alan Wallace comments on the Dzogchen understanding of the substrate consciousness and how to relate to appearances. Follow along with the text starting on page 149 in the PDF of the root text (found in Lesson 1) or in your copy of Heart of the Great Perfection, or in the excerpt below.
With those words she dissolved, together with the mirror, into my heart, and my body, speech, and mind were filled with joy and bliss. Those [words] were my rationale, so once again I ardently meditated on luminosity and cognizance. Consequently, at times it seemed as if that which appeared and that which was aware nondually dispersed outward [476] and then converged inward again. On other occasions, that which appeared and that which was aware were nondually and spontaneously objectified and then naturally disappeared. At other times appearances and awareness were nondually self-emergent and self-dissolving, such that I understood that they were not projected out from within the body. I knew that these experiences were attributable to grasping at the ground of being as an object. (more…)