A Direct Pointer to Direct Experience
The Direct Experience of Reality (in Sanskrit Aparokshanubhuti) is a short classic text on the non-dual teachings. It was once thought to have been written by the original Shankara Acharya, who probably lived in the eighth century and gave what is still the most complete and respected presentation of the non-dual philosophy. Most scholars now believe that this text was in fact written later by a close follower of Shankara. It is seen as a succinct and relatively simple introduction to the essential teachings, one which may be helpful to those who find it difficult or unnecessary to follow the longer and more complex works, such as Shankara’s commentaries on the Upanishads and the Bhagavad Gita.
Direct Experience of Reality is indeed relatively short. But this brevity is due to the fact that it does not dwell on much of the discussion and illustrations that are elsewhere used to convey and explain the teachings. It will appear simple if we are ready to hear the essentials given in the most direct way and to understand the subtleties without elaboration.
One passage emphasises the difference between the true Self (Atman) and the physical body. The reason for this emphasis is to make clear that the body is not the Self. At the beginning of the path we have the strong feeling of identity with the body and sense-experience, this is the root of egoity, and this conviction has to be challenged.
The text then goes on to say that in Reality there are no differences, and that the physical body (and by extension the physical world) are not different from Atman.
These are two central points in the non-dual teachings. First: the body is not your true Self, the two are different in kind. If this were not true, we could never be entirely free of the limitations, sufferings and mortality of the physical body. Second: in Reality there are no differences, there is only Atman. If this were not true, the principle of non-duality would be contradicted, there would be more than one reality, which is absurd and would obviate the possibility of ultimate knowledge.
It cannot be denied that the body and the natural world appear in our experience. The world is full of separations, diversity and change. Our bodies and mind are similarly composed of many parts and constantly change and one day will go through the radical change called death. In this way they are different from that which we call ultimate reality, the absolute, God, Brahman, because That is not many, does not change, and knows neither birth nor death.
How then can it be that the body is different from the Self, while in Reality there are no differences?
The difficulty of providing a satisfactory answer to this question is what has led some thinkers to believe that the non-dual teachings are mistaken and to accept a form of duality. One school of thought that was influential in Shri Shankara’s own time held that matter and consciousness are both real and eternal and that spiritual illumination is achieved when consciousness is entirely distinguished from matter.
But this view implies that there are two realities, which, as we noted earlier, is rationally unacceptable, and in practice it would mean that real knowledge and liberation are impossible.
The solution offered by Shri Shankara is that anything which appears to be different from Atman is an appearance, and appearance and Reality are not two, because one is real and the other is apparent.
This is the subtlety at the centre of the text, and of the non-dual philosophy. It is not merely abstruse logic-chopping. In our reflections and meditations, it is important to have understood that the appearances we experience through our mind and senses are not the absolute Reality, and yet that nothing exists that is different from absolute Reality. Let us see how Aparokshanubhuti leads up to and presents this matter with such brevity and directness.
The text begins by reminding us that we will only be able to follow this teaching if we have developed some qualities that make the conditions of our inner world suitable for the cultivation of higher knowledge. These qualities are summarised as: discernment, detachment, self-control and an overriding desire for liberation.
Much could and has been said about each of these qualities, and on the path we have to apply them in a balanced, cheerful, progressive way of life. For now let us note that we cannot expect all our questions to be answered philosophically without us working carefully on the condition of our mind. Then:
One with these qualities should practise enquiry (vichara in Sanskrit) to achieve knowledge of truth, the highest good. [Direct Experience of Reality verse 10]
The central practice on the path of non-duality is a life of enquiry into the nature of Self and Reality. The bondage we experience is caused by ignorance, not knowing our true nature. The solution to ignorance is knowledge, and knowledge comes through enquiry. Vichara includes asking questions:
What am I? How is the world created? Who is its creator? What is its material cause? This is the reasoning called cogitation (vichara). 
This enquiry also involves reasoning along the lines indicated by the teachings. Another verse says:
The whole world is a product of nescience; it disappears with the dawn of true knowledge. Its real creator is mental activity of many kinds. This is the reasoning called cogitation (vichara). 
Many volumes of teachings are distilled into this one verse. It says that the world as we experience it arises from a kind of not-knowing, an erroneous view. The ultimate origin of the phenomenal world is not a physical process but more like the rise of an appearance, brought about by mental activity. This is central to the philosophy because, as we saw, if the changing, diverse world and the unchanging, non-dual Atma-Brahman were both real, then there would be two realities, which is impossible. And if the world of change and limitation were absolutely real, there could never be complete freedom from it.
We might ask further what are those ‘various kinds’ of mental activity? Does this refer to the sum total of the workings of all the individual minds, or something more than that? It is certainly true that all of a person’s experience of the external world happens through that person’s mind. So in this sense it is clear that the world as it is experienced by the individual, is formed by the mind.
But this does not mean that there is no external world beyond the contents of the mind. Shankara is clear that objects exist independently: he says that in perception the mind assumes the form of objects in a way analogous to the way in which molten bronze assumes the form of a mould, or pure light assumes the colours of what it illumines.
So is ‘mental activity of various kinds’ also the real creator of the objective world that exists independently of our mind? If we think of that world as having qualities, such as names and forms, we are in fact projecting onto it qualities as they are presented to us by our senses and mind. And if we ask, ‘where does the external world come from: who or what created it?’, we are assuming that space and time and causality as they occur in our experience, apply to what is unaffected by the limits of our experience.
So we find that the world, as we experience it, is the product of thought. And we also find that our attempts to conceive of whatever exists beyond our experience are also bound and formed by the way our mind works. Therefore it is concluded that the whole world considered as separate from the Supreme Being, is created by ‘mental activity of various kinds’, and this ‘not-knowing’ will end only with the rise of true Knowledge. All this is condensed into paragraph 14 of our text. The next says:
As clay is the material cause of a pot, so is the subtle, imperishable truth absolute the material cause of these two (not-knowing and thought). This is the reasoning called cogitation (vichara). 
At first we might question the validity of this statement. Does it not contradict what has gone before? Does it mean that the world has a real cause? Is it saying that truth absolute is involved in action and change? These are both contradictions of the non-dual principle.
On further reflection we see that these criticisms do not apply, because this verse does not speak about the origin of the world. It states only, and precisely, that the subtle truth absolute is the material cause of not-knowing and thought. As we noted before, not-knowing and thought are appearances, they are not independently Real. Therefore, their ‘creation’ too is ultimately apparent, not absolute, and to speak of their creation does not imply that Reality is limited by it in any way. At the same time, this verse does not suggest that the origin of all we experience is anything other than truth absolute, the supreme aim of our devotion and seeking. Then:
It is a most undoubted fact that I am the One who is subtle, the knower, the witness, truth and imperishable. This is the reasoning called cogitation (vichara). 
The word I here means not the individualised mind with its sense of ego, but pure consciousness. This is the Real, not the apparent. Thus the identity of the true I of the seeker, and the Real that is sought, is expressed with the concise directness that characterises all of this text. Brief as it is, it will more than repay careful attention and long contemplation.