Now suppose that in the autumn—when it’s raining in fat, heavy drops—a water bubble were to appear & disappear on the water, and a man with sight were to see it. To him it would appear empty, void, without substance: for what substance could there be in a bubble? In the same way, a man with wisdom sees a feeling. To him it would appear empty, void, without substance: for what substance could there be in a feeling?

The Buddha gives a series of similes for the aggregates: physical form is like foam, feeling is like a bubble, perception is like a mirage, choices are like a coreless tree, and consciousness is like an illusion.