The concept of Nonduality can be understood in several ways, but generally it involves the nonexistence of an individual self: 

In the seen there is only the seen, 
in the heard, there is only the heard, 
in the sensed there is only the sensed, 
in the cognized there is only the cognized: 
This, Bāhiya, is how you should train yourself. 

When, Bāhiya, there is for you 
in the seen only the seen, 
in the heard, only the heard, 
in the sensed only the sensed, 
in the cognized only the cognized, 
then, Bāhiya, there is no ‘you’ 
in connection with that. 

When, Bāhiya, there is no ‘you’ 
in connection with that, 
there is no ‘you’ there. 

When, Bāhiya, there is no ‘you’ there, 
then, Bāhiya, you are neither here 
nor there 
nor in between the two. 
This, just this, is the end of suffering.  
~ Ud 1.10 

According to the teachings on Dependent Origination (paṭiccasamuppāda) and Emptiness (Śūnyatā), all phenomena are conditioned, impermanent, and without inherent existence. This includes all mental phenomena, particularly the personal self, or ego.  

However, many people interpret nonduality to mean that there are only experiences with no individual experiencer. There is no “you there,” only phenomena exist.

All this seems to make sense, except for the fact that it is not possible to have an experience without an experiencer—even for a Buddha. This is because, as the phenomenologist Edmund Husserl discovered, “consciousness is always a consciousness of something.” In other words, consciousness is always a point of view.

Experiences without an experiencer would be an un-self-consciousness. This only occurs with animals, being pure awareness without self-awareness.

The philosopher Emanuel Kant (b.1724, d.1804), pointed out that we are only conscious of appearances, or the effect that things have on consciousness. We can never know what lies beyond the conscious experience itself, or what things in themselves truly are.  

For example, the redness and taste of an apple result from contact with nerve receptors. We do not see or taste the apple in-itself. All the physical qualities of the apple are expressed as nerve impulses in the brain. In other words, we can never know what that object really is, only as it appears. It is the same with all sense experience and the thoughts they produce.

This means that all experiences are made of consciousness. All we know is consciousness. What lies beyond the conscious impression is unthinkable.

If this is difficult to understand, close one eye and with your finger push on the side of the open eye. You will notice that the object you are looking at moves when you push the eye with your finger. This can only occur because the image exists in the mind. How else could the image move? You are never seeing the world directly, but only as it appears to your mind. All that we know to exist, exists only to individual consciousnesses.

It is in this sense that reality is nondual. All experience, everything that exists, is mind dependent. It is dependent on someone’s observing mind.

Since everything is mind dependent, then everything is empty of any inherent existence. Everything is Sunyata, or emptiness.

But then, what does the Buddha mean by, “there is no ‘you’ there”? How can this nonduality be understood? 

What the Buddha means is that the “you” (the self or ego) is a creation of the mind. It is made of thoughts and memories. It is another object of a knowing consciousness, and empty of inherent reality:  

Bhikkhu, ‘I am’ is a conceiving; ‘I am this’ is a conceiving; ‘I shall be’ is a conceiving; ‘I shall not be’ is a conceiving; ‘I shall be possessed of form’ is a conceiving; ‘I shall be formless’ is a conceiving; ‘I shall be percipient’ is a conceiving; ‘I shall be non-percipient’ is a conceiving. ~ MN 140.31 

When the Buddha says, “you do not exist,” he is referring to the mundane “you.” The self that is constructed from thoughts and memories (which are objects of a consciousness), a conceiving.  

By saying, “in seen there is only the seen,” he means to be aware of the seen simply as objects of awareness, or without a reference to the self. It is not desiring nor disliking things with respect to what they mean to you. Existence is just existence. It is the mundane self that gives it qualities, like pleasant or unpleasant, good or bad, beautiful or ugly.

Buddhism becomes difficult, in fact almost impossible, when you think that nothing truly exists, not even your individual awareness. If nothing exists then everything is meaningless, including Buddhism. In this sense, Enlightenment is only Nihilism.

The knowing consciousness, or the awareness, knows everything that exists as a conscious experience. Pure awareness is Unconditioned consciousness. The Unconditioned becomes conditioned when it gets involved with the world, becoming the “I.” 

The Buddha often insisted that all he taught was the cause of suffering and the end of suffering. That is the Four Noble Truths and the Eightfold Path. It is best to keep it simple.

The following is a talk by the late Thai Buddhis monk Ajahn Chah. He was renowned for his down-to-earth yet deep penetrating wisdom: 

When the mind transcends conditions, it knows the unconditioned. The mind becomes unconditioned, the state which no longer contains conditioning factors. The mind is no longer conditioned by the concerns of the world, conditions no longer contaminate the mind. Pleasure and pain no longer affect it. Nothing can affect the mind or change it, the mind is assured, it has escaped all constructions. Seeing the true nature of conditions and the determined, the mind becomes free. . .

The tendency to conceive things in terms of self is the source of happiness, suffering, birth, old age, sickness and death. This is the worldly mind, spinning around and changing at the directives of worldly conditions. This is the conditioned mind. . .

We should clearly understand these determinations. Good, evil, high, low, black and white are all determinations. We are all lost in determinations. . .

If we know the truth of determinations clearly, we will know that there are no beings, because ‘beings’ are determined things. Understanding that these things are simply determinations, you can be at peace. . . This is true merit, to be calmed of proliferations, calmed of ‘being,’ calmed of individuality, of the burden of self. Transcending these things one sees the unconditioned. This means that no matter what happens, the mind doesn’t proliferate around it. ~ Ven. Ajahn Chah, ‘Toward the Unconditioned,’ in ‘Food for the Heart.’ 

The Unconditioned mind is just your pure awareness, pure knowing. It is pure because it knows but does not need anything it knows. It is marked by simplicity and peacefulness.  

Every individual is a point of view of pure awareness. In this sense, we are all Buddhas in the making.