Found this great essay online which addresses a large number of issues raised within this discussion, so I’m taking the liberty of posting the entire essay below. 
# Nonduality – Defining the Undefinable By Michael W Taft
What Is Nonduality?
Nonduality is the human experience of oneness with all things; a sense of connection to and identity with the entire universe. It is intimacy with everything. In this experience, the sense of being a witness or seer of things vanishes completely, and instead you feel yourself to be whatever thing you are beholding. You don’t see the mountain, you are the mountain. You don’t hear a bird, you are birdsong. Awareness is no longer split into a experiencer and the thing that is experienced, there is just pure experience with no divisions. This experience of connection is the essence of nonduality.
How to Have an Experience of Nonduality
Every culture worldwide has known about nonduality, and they have developed hundreds of techniques to help human beings to have this experience. (If you want to give one of these a try, click here.) But one of the many things that makes nonduality so fascinating is that you don’t actually have to do a practice at all to experience it, because it’s not a kind of altered state or religious vision. Instead, the experience of nondual awareness is an essentially human one.
Perhaps it is true, as many nondual philosophies have insisted, that nondual awareness is actually at the root of all human awareness. Maybe nondual awareness is simply there , in all of our experience like a spleen or a leg bone, for anyone who looks deeply enough to discover.
So while it’s possible to do special meditation practices to induce nondual awareness (or maybe we should say to reveal nondual awareness), and I recommend that you do that if you’re interested, it’s also the case that many people only need to have their always-already-existing nondual awareness pointed out to them to have at least a little taste of it. Whether you get their via meditation or via “pointing out,” however, nondual awareness is something that underlies all your perceptions of yourself, the world, and the transcendental. It’s there for you to find, if you want to go looking.
Nonduality in Religion
There are some religions, such as Hinduism and Buddhism that have concepts of nonduality at the core of their belief systems. Other religions and philosophies include at least a branch that is concerned with a nondual view. Even indigenous cultures and shamanism talk about such a view of the world.
Because nonduality is at the core of human experience, most groups of people get around to talking about it at some point. However, there was one place in the world where culture became utterly captivated by ideas about nonduality and methods for achieving (or revealing) nondual awareness, and that was in the Indian subcontinent. Indian culture became strongly focused on nonduality, as you can see from the religious terms used for it.
In Hindu contexts, nonduality is called advaita , which literally means “not-two-ness” and is the source of the English word nonduality. Usually Hindu nonduality involves oneness and identity with God(dess), and so is a deity-based practice.
In Buddhist tradition, nonduality is called no-self ( anatta ), emptiness ( shunyata ), or rigpa . The theories of Buddha Nature and Tathagatagarbha talk about why nonduality exists or what it means, and unlike Hinduism is non-deity-based (i.e. it is not about God).
All human cultures everywhere have experienced and described nonduality and nondual experience, but ancient India became particularly focused on it.
If you want to learn more about the history of nonduality in Indian religion, click here.
Nonduality and Awakening
To say it simply, nonduality is the essence of awakening; what is also called enlightenment, liberation, realization, divine union. When a person has a strong nondual experience, they have begun the process of awakening. For most people this process takes an entire lifetime, and is always growing deeper and broader, encompassing more and more areas of their life.
Because in a religious context nondual awakening is considered to be the ultimate salvation, Indian religious are extremely focused on ways to gain this salvation. It is somewhat similar to the way Christian religion became obsessed with ways to gain the salvation of Heaven (although also different in important ways).
In short, if you have any interest in “getting enlightened,” then what you are actually looking for is an experience of nondual awareness. Because nondual awareness is at the base of the mind, a first experience of nonduality—however minor, fleeting, or shallow—is luckily not all that difficult to achieve (or notice).
After that, it becomes a process of deepening and expanding your nondual awareness to affect all areas of life. The profoundity of access to nonduality in daily life is what distinguishes spiritual dabblers from the heavyweights.
Is Nonduality Some Kind of Ultimate Reality?
In most religious descriptions of nonduality, it is described as the ultimate reality. The extent to which you contact nondual awareness is the extent to which you contact God, the Universe, and Everything. Another way to say this same idea is that “consciousness is everything.”
But is this really true?
In short, any assertion about ultimate reality is untestable by definition. That means that nobody can prove whether nonduality is the ultimate reality or whether consciousness is everything. No matter how much you believe that to be true or believe it to be a fantasy, there is literally no way of testing, proving, or knowing whether you’re right.
In one way of looking at it, having the experience proves that it’s real, at least to the satisfaction of the person to whom it’s happening. If you have a deeply spiritual experience of oneness with all things, which utterly revolutionizes your life, and transforms your interactions with everyone else, who cares whether it’s real in some scientific sense? It’s certainly real enough in the ways that matter.
However, there is another way to look at it.
How Does Nondual Awareness Arise?
The basic understanding of nonduality in a religious context is that it is the true, real view of ultimate reality. Because everything is made of consciousness, to see that everything is one in awareness is to see ultimate reality.
But let’s talk about the same experience in a different way for a moment.
From a scientific viewpoint, a human being only knows about their environment through the senses. For example, you don’t see the world directly through your eyes, as if you’re inside your head looking out two open windows. Instead, the eyes function very much like video cameras. The photons from the exterior world stream through the lenses and strike the retinas. The cells of the retina convert these photon strikes into electrical pulses which are then sent down the optical nerve deep into the brain.
These electrical pulses represent digital information about the visual field outside the eyes. The brain then decodes this digital information through many layers of pre-processing and processing until it is eventually assembled into a mental image of the outside world. It is this mental image that arises in consciousness.
Therefore, you never see the outside world. You have never seen the outside world in your entire life. You only see your constructed mental representation of decoded signals from the eyes.
And it is the same for all the other senses. The ears encode air waves, which the brain decodes into the experience of sound. The nose and tongue encode chemical signatures, which the brain decodes into smell and taste. The skin encodes pressure, heat, and so forth, which the brain decodes into touch.
Therefore, you have never experienced the world directly in any way. You have only experienced the constructed mental representation of decoded signals from the senses. If you understand this fundamental point, you understand how “the entire world is consciousness.” Because your experience of the world always arises only in consciousness, it would be more accurate to say “ my experience of the entire world is consciousness.”
For the same reason that you cannot prove that nonduality is ultimate reality, you cannot prove that the above description is ultimately true. It does have the advantage of being scientifically provable, however. It also has the very big advantage of removing a tremendous amount of confusion, superstition, and wasted time. You can read more about that here. And here.
In the end, it probably doesn’t matter which view of nonduality you believe is real (“consciousness is everything” or “the experience of consciousness is everything”). The important thing is to contact nondual awareness, because doing so is a life-changing capacity.
Does a Nondual Experience Require Effort?
Another big controversy concerns what a person has to do to have an experience of nonduality. Because from a spiritual viewpoint, nondual awareness underlies everything, and is always already there at the base of all experience, it’s possible to state that absolutely nothing need be done to experience it. It’s already there and you’re already experiencing it. You just have to notice it. This is the “effortless” model.
A second way of looking at it is the “effort” model, which says that while, yes, nondual awareness underlies everything, there are a lot of layers of belief, psychological blockages, and simple ignorance getting in the way of seeing this experience. The purpose of meditation and other practices is not to create awakening, but to remove what is blocking the experience of the nondual awareness that is already there. Even if you’ve already had a strong nondual experience, the deepening of your awakening requires more effort.
Proponents of the effortless model say that even making an effort at all is just putting more blockages in the way of seeing the nonduality that is already there. The very act of meditating to “get something,” they say, is paradoxically just one more thing that’s getting in the way of direct perception of ultimate reality.
Proponents of the effort model say that very often people who pursue the effortless path don’t have very deep awakening. They see the effortless model as being more about developing a concept of nonduality—i.e. being able to talk about it, and being very concerned with language around it—rather than developing actual depth of nondual experience.
Given that this (ironically dualistic) dichotomy has been discussed for thousands of years without reaching a conclusion that is satisfying for everybody, we can say with confidence that you have to choose for yourself which side you feel more drawn towards.
Even better would be to let go of the need to see either one as right or true or the best, and simply notice the nonduality at the center of the apparent dichotomy.
Talking about Nonduality
Nonduality contains within it a lot of paradoxes. This is only natural when you think about it, since a paradox is something that contains apparent opposites—and the essence of nonduality is the union of opposites.
One of the big paradoxes is that it’s hard to talk or write about correctly. Almost any language you use is actually incorrect, misleading, or contains dualisms.
For example, even simple statement in the above text such as “having a nondual experience” are slightly misleading. Think about it. If nondual awareness, as described above, means the collapse of the experiencer and the experienced, the seer and the seen, then in precise language it may not be correct to call nondual awareness an experience at all.
Even apparently simple ideas in the text above, such as the “external world” don’t really make sense in the mode of nonduality. For there to be an external world, there needs to be an internal world, and those two things need to be opposite and different—which of course they are not in nondual awareness.
The simple fact is that language is inherently dualistic, and there’s no way to say anything intelligible if you try to talk about nonduality from an absolutely nondual perspective. It cannot be done, and yet it is important and useful to talk about nonduality. Therefore, in this article I’ve chosen to just go ahead and talk about it from a normal, dualistic perspective.
Conclusion
Nondual experience is something that is always available, and also something that you may spend the rest of your life cultivating, deepening, and integrating into your everyday experience. It’s very helpful to find someone who can point it out to you with confidence and clarity, since it’s easy to mistake various other experiences for nonduality. Just like some of the more famous internet memes, nondual experience is something that, once seen, it cannot be unseen. You and your relationship with other people and the world are forever changed.
