The Emptiness of Phenomena is not Nonexistence (from Nagarjuna’s Mulamadhyamakakarika, by Jay L. Garfield, in Buddhist Philosophy, Essential Readings, edited by William Edelglass and Jay L. Garfield, Oxford and New York 2009)
That all phenomena are dependently originated is the heart of Buddhist ontological theory. In the Mahayana tradition, this dependency is spelled out in three ways: all phenomena are dependent for their existence on complex networks of causes and conditions; a dollar bill, for instance, is dependent on the printing press that printed it, the miners who extracted the ore out of which the metal for the press was smelted, the trees that were pulped for the paper, the United States Treasury, and so on. All wholes are dependent on their parts, and parts on the wholes they help make up. The dollar bill depends for its existence on the particles of paper and ink that constiture it but also, for its existence as a dollar bill, on the entire economic system in which it figures. Finally, all phenomena are dependent for their identities on conceptual imputation. The dollar bill is only a dollar bill, as opposed to a bookmark, because the United States Treasury so designates it. To exist, according to Buddhist metaphysics [sic], simply is to exist dependently in these senses, and hence to be merely conventionally existent.
To exist dependently is, importantly, to be empty of essence. For a Madhyamika, like Nagarjuna, this emptiness of essence is the final mode of existence of any phenomenon, its ultimate truth. For to have an essence is to exist independently, to have one’s identity and to exist not in virtue of extrinsic relations, but simply in virtue of intrisic properties. Because all phenomena are interdependent, all are empty in this sense. Just as the conventional truth about phenomena is made up by their interdependence, their ultimate truth is their emptiness. These are the two truths that Nagarjuna adumbrates throughout his corpus.
It follows immediately that the emptiness of all phenomena that Nagarjuna defends is not nonexistence: to be empty of essence is not to be empty of existence. Instead, to exist is to be empty. It also follows that emptiness is not a deeper truth hidden behind a veil of illusion. The emptiness of any phenomenon is dependent of the existence of that phenomenon, and on its [inter]dependence, which is that in which its essenceless consists. Emptiness is itself dependent, and hence [also] empty. This doctrine of the emptiness of emptiness, and of the identity of interdependence, or conventional truth, and emptiness, or ultimate truth, is Nagarjuna’s deepest philosophical achievement. The two truths are different from one another in that the ultimate is the object of enlightened knowledge and liberating, while the conventional is apprehended by ordinary people through mundane cognitive processes. Nonetheless, they are in a deep sense identical. To be empty of essence is simply to exist only conventionally. The conditions of conventional existence are interdependence and impermanence, which, as we have seen, for Nagarjuna, entail essencelessness.