What Are the Inner and Outer Consciousness-Minds?

If the mind is divided into inner and outer, the outer mind refers to the mind consciousness that sentient beings can generally discover and observe, while the inner mind refers to the mind root (manas) that sentient beings find difficult to discover and observe. The two conscious minds are one manifest and one hidden, one bright and one dark, one deep and one shallow; one is easily changed, the other is firm and hard to change. Cultivation means first putting practice into effect at the shallow level of the mind consciousness, and then at the deep level of the mind root—first preliminarily transforming the mind consciousness, and finally and ultimately transforming the mind root. Therefore, all afflictions and ignorance are, at first and most evidently, at the level of the mind consciousness, and, at last and most hidden and profound, at the level of the mind root.

From this sūtra we can see that although the Buddha, when teaching the Small Vehicle Dharma, did not explicitly speak of the Dharma of the mind root, He nevertheless implicitly touched upon the mind root, implicitly teaching that all afflictions and ignorance belong to the mind root; that eliminating afflictions means eliminating the afflictions of the mind root; that liberation is the liberation of the mind root; and that all dharmas must be put into effect at the mind root. If the problem of the mind root is resolved, all dharmas can be resolved, and one can ultimately and thoroughly attain nirvāṇa and liberation.