Is There Discernment of the Five Consciousnesses in Dreams?

The realms experienced in dreams are all mere-shadow states, entirely within the realm of dharma-dust. They lack the relatively more substantial substantive states of the five dusts. Due to the absence of these five dusts, the mere-shadow state is incomplete and deficient. The solitary mental consciousness, when cognizing dharma-dust alone, does so indistinctly; it is approximate and profoundly illusory and unreal. Therefore, both consciousness and the mental faculty cannot cognize things clearly, making errors unavoidable. Sometimes these errors are particularly numerous and significant, often leading to confusion of one thing with another. In dreams, the mental faculty dominates the process of cognition. The mental faculty's wisdom in cognizing unfamiliar realms is weak, lacking accurate discernment, so the dharmas it cognizes are unclear and indistinct.

If the realm of the five dusts were present in dreams, the five consciousnesses would participate in cognition. Then there would be no difference from the waking state, and consequently, there would be no dream state and no sleep.