Half Empty of What?
If I am holding a cup of water and I ask you, "Is this cup empty?" you will say, "No, it is full of water." But if I pour out the water and ask you again, you may say, "Yes, it is empty." But, empty of what? . . . My cup is empty of water, but it is not empty of air. To be empty is to be empty of something. . . . When Avalokita [Avalokiteshvara, the bodhisattva of compassion] says that the five skandhas are equally empty, to help him be precise we must ask, "Mr. Avalokita, empty of what?"
The five skandhas, which may be translated into English as five heaps, or five aggregates, are the five elements that comprise a human being. . . . In fact, these are really five rivers flowing together in us: the river of form, which means our body, the river of feelings, the river of perceptions, the river of mental formations, and the river of consciousness. They are always flowing in us. . . .
Avalokita looked deeply into the five skandhas . . . and he discovered that none of them can be by itself alone. . . . Form is empty of a separate self, but it is full of everything in the cosmos. The same is true with feelings, perceptions, mental formations, and consciousness.
--Thich Nhat Hanh, The Heart of Understanding