So different minds can exist, representing different consciousnesses that each produce the world, even though the external world itself is ultimately empty.
Each mind is like a mirror, and so although the world that they reflect from consciousness is not real, the minds (mirrors) are real.
The Consciousness-Only school’s mode of discussion was quite new in Chinese thinking. In its abstraction, it was very different from “this-worldly” Chinese thinking. For this reason, this school eventually declined.