Ignorance (avidyā) is not a truly existent dharma; it has no real substance, and therefore it can be eliminated, whereas truly existent dharmas cannot be eliminated—for example, the tathāgatagarbha, the self-nature of suchness. Wisdom and ignorance stand in opposition to each other: where there is ignorance there is no wisdom, and where there is wisdom ignorance disappears. When ignorance is completely extinguished, the ālayavijñāna is transformed into the undefiled consciousness (amala-vijñāna). Before the eighth bhūmi, because the ignorance of the first seven consciousnesses is heavy, the tathāgatagarbha is called the ālayavijñāna, meaning that sentient beings at this stage still carry the karma of segmented birth-and-death within their seven consciousnesses and five aggregates (pañcaskandha). Wisdom is born later, corresponding to ignorance, and is a dharma subject to arising, ceasing, and change. But the wisdom of all Buddhas never regresses and never perishes, just as a Buddha will never change back into a sentient being.
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