Emptiness is another kind of nondual teaching. Emptiness teachings demonstrate that the "I," as well as everthing else, lacks inherent existence. The notion of lacking inherent existence has several senses. In one sense, empty things lack essence, which means that there is no intrinsic quality that makes a thing what it is. In another sense, empty things lack independence, which means that a thing does not exist on its own, apart from conditions, relations or cognition. A great deal of what one studies in the emptiness teachings demonstrates the relations between these two senses, and heightens one's sensitivity to their ramifications.
According to Buddhism, when emptiness is realized, peace ensues. One's experience is transformed so that the self, other beings and the world no longer seem like intrinsically compartmentalized objects, distinct and separate from each other. The self and all things are experienced as free.
If the selflessness of phenomena is analyzed
and if this analysis is cultivated,
It causes the effect of attaining nirvana.
Through no other cause does one come to peace.
(The Samadhiraja Sutra)
One who is in harmony with emptiness
is in harmony with all things.
(Nagarjuna, Treatise on the Middle Way 24.14)
How Is Emptiness Nondual?
The most common connotation of "nonduality" is "oneness" or "singularity." Many teachings state that everything is actually awareness; those teachings are nondual in the "oneness" sense in which there are no two things.
But there is another sense of "nonduality." Instead of nonduality as "oneness," it's nonduality as "free from dualistic extremes." This entails freedom from the pairs of metaphysical dualisms such as essentialism/nihilism, existence/non-existence, reification/annihilation, presence/absence, or intrinsicality/voidness, etc. These pairs are dualisms in this sense: if you experience things in the world in terms of one side of the pair, you will experience things in the world in terms of the other side as well. If some things seem like they truly exist, then other things will seem like they truly don't exist. You will experience your own self to truly exist, and fear that one day you will truly not exist. Emptiness teachings show how none of these pairs make sense, and free you from experiencing yourself and the world in terms of these opposites. Emptiness teachings are nondual in this sense.
Emptiness in Buddhism
According to Buddhist teachings, freedom from suffering dawns when we realize that we ourselves, as well as all things, are empty.
In Buddhism, suffering is said to come from conceiving that we and the world have fixed, independent and unchangeable natures that exist on their own without help from anything else. We expect that there is a true way that self and world truly are and ought to be. These expectations are unrealistic and prevent us from granting things the freedom to come and go and change. We like pleasant things to abide permanently, and unpleasant things to never occur. We experience suffering when we actually encounter comings, goings and change. Suffering often takes the form of anger, indignation, existential anxiety, and even a sense that, as they say in TV sitcoms, "something is wrong with this picture."
But when we deeply realize that we and the world are empty, we no longer have unrealistic expectations. We find peace and freedom in the midst of flux.
What Does Emptiness Mean?
What are things empty of? According to the Buddhist teachings, things are empty of inherent existence.
Being empty of inherent existence means that there is no essential, fixed or independent way in which things exist. Things have no essential nature. There is no way things truly are, in and of themselves. Different Buddhist schools or tenet systems have different ways of characterizing emptiness; they have different ways of helping students reduce suffering. My characterization of emptiness adheres somewhat to the Tibetan Gelug-ba school of Prasangika. This is not the only tenet system in Buddhism that discusses emptiness. There are other schools with slightly different interpretations of the emptiness teachings.
I prefer the Tibetan Prasangika interpretation for pragmatic reasons. It has a greater number of publically available supports for studying and meditating on emptiness than I have seen in other Buddhist schools. The term "Prasangika" is Sanskrit for "consequence." The "consequence" designation comes from this school's method of debate and refutation, which follows Nagarjuna's style in his Treatise.