Or one can say that the One Mind is like the ocean, and the phenomena are the waves. The ocean is not just all the waves; it is something greater in its own right.
The Principle is ultimately the principle of emptiness / the lack of an inherent nature, which is the true nature of all phenomena.
The One Mind is stillness, eternal, unchanging, beyond action and non-action, imperceptible, beyond origination and disintegration, etc.
The many phenomena of the worlds (from our minds) are active, temporary, changing, having action and motion, perceptible by the senses, subject to birth and death, etc.