Having already said that the five skandhas were empty, why does the Buddha now specifically declare the emptiness of each of the five skandhas—form, sensation, perception, volition, and consciousness? Because he wanted people to understand that true emptiness is total, encompassing all physical and mental realms. The Buddha makes it clear that he is talking about ultimate emptiness—emptiness as reality—and not self-centered emptiness, analytical emptiness, or emptiness of only the self.

Emptiness of Form

The Heart Sutra speaks from the standpoint of the Mahayana idea of ultimate emptiness. The Buddha says that the five skandhas are not separate from emptiness, that they are indeed empty. Form is emptiness because it does not exist in a definite, enduring location; nor does it have an enduring shape or appearance. Forms, whether atoms or planets, interdependently exist and interact with all other forms. This is the only way we can know of their existence. If something had an eternal, unchanging, independent nature, it would never react with anything else, and, hence, we would never become aware of its existence.