At the core of one of the most important Zen Buddhist texts, the Heart Sutra, is this declaration:

Form does not differ from emptiness,
emptiness does not differ from form.
That which is form is emptiness,
that which is emptiness form.
The same is true of feelings,
perceptions, impulses, consciousness.

One of the most famous expressions of the concept of non-duality, the Heart Sutra is but one example of an idea that humans have alternately embraced and dismissed for millennia. What is non-duality, then, and why do we find it both unsettling and desirable?

What is non-duality? What is the difference between duality and non-duality?

Dating back to the ancient Indian religious scriptures, the Upanishads, non-duality is an idea used in not only spiritual, but also psychological and even scientific contexts. Different traditions define non-duality differently, but in essence, non-duality sits in the space between monism, or singleness, and dualism, which holds that all experience can be boiled down to just two, mutually exclusive, parts. 

The term “non-duality” is used variously to describe:

• the nondifference between self and other;
• the ultimate nature of reality; 
• the non-separateness of all things; 
• the transcendent relationship between opposites, and 
• the mystical union of God and humans.

Examples of dualism include mind and body, subject and object, even the ideas of here and there. In theology, dualism describes the basic, abiding principles of good and evil. Non-duality is outside the realm of human logic and language, though many have tried to describe and reason it out. 

In the secular realm, the Ancient Greek neo-Platonic philosopher Plotinus held that there is an ultimate reality underneath everything that is unique and requires no explanation. So simple as to be indescribable, this principle is like the color white, which contains all the other colors, yet is defined by not being all those other colors.

Beginning in the eighteenth century, science embraced a dualistic view of an entirely material universe composed of irreducible opposing principles. This gave rise to the concept of science as agnostic, an approach that cannot consider any evidence beyond material phenomena that is observable and measurable. Today, some scientists—stymied by science’s inability to explain fundamental mysteries including the nature of consciousness, and influenced by the entanglement theories of quantum physics—are beginning to consider the validity of accepting non-material considerations into the scientific model. 

Poet William Blake famously explored the paradox of dualism. In The Marriage of Heaven and Hell, he pointed to the union of opposites as necessary without trying to explain non-duality: “Without contraries is no progression. Attraction and repulsion, reason and energy, love and hate, are necessary to human existence.”

As philosophers, poets, and scientists suggest, life is more connected than it appears on the surface. And it is the human condition to seek connection and a sense of wholeness. Some trace our sense of alienation back to when we came to see nature as separate from us, others to the psychological experience of the separate self.

Carl Jung’s theory of the collective unconscious reflects a non-dual state in that it holds that all people have a set of shared memories and ideas. Nondual therapy holds that the concept of the separate self is an illusion and seeks to help people tap into the experience of wholeness.

What religious traditions believe in non-duality? 

The concept of non-duality or non-dualism is perhaps the central principle of the world’s wisdom traditions. In the major Eastern religions, however, there are subtle, but important differences in how non-duality is perceived. In Hinduism, advaita is a Sanskrit word that means “not two-fold.” The Vedanta concept of non-duality contains both a self and a deity. This philosophy holds that the individual self (atman) and the ground of reality (brahman) can come together as one substance (God). In the tradition of Advaita Vedanta, to reach this state of awareness is to move to a transcendent state beyond self to pure consciousness. The non-duality attained through yoga practice is not aimed at merger with a deity, but rather toward the integration of mind and body within the atman.

Advaya is a Mahayana Buddhist term meaning “that which is without duality.” It refers to the ultimate truth, not defined by opposites such as self and other, or subject and object. Knowing non-duality is a form of consciousness attained through enlightenment. There is no deity or God in the Buddhist tradition, just as there is no self or other.

What does non-duality feel like? How do you experience it?

The experience of non-duality can come upon us at any time. The younger we are, the less developed is our sense of a separate self, and our consciousness is much more merged with experience. We may recall fragments of this feeling when we gaze up at clouds, for example, or out over ocean waves. The longing to return to this feeling of limitless unity is a basic feature of human experience.

• Countless spiritual traditions use meditation techniques to attain the transcendent sense of oneness.
• A. H. Almaas, the founder of the Diamond Approach spiritual path, believes that humans become alienated from their true nature by living in the world. Through inquiry and meditation, practitioners can come to an experiential understanding of non-duality and a reconnection with their true nature.
• Psychedelic substances including psilocybin and ayahuasca have been used in religious ceremonies for millennia to facilitate mystical or spiritual encounters with the Divine.
• There are also techniques for spontaneous non-dual awareness including the English philosopher and mystic Douglas Harding’s “Headless Way” of dissolving the boundaries between ourselves and the universe.

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