You may have heard the terms 'the witness state', 'being the witness' or 'perceiving as the witness' being used with regards to spirituality and Non-Duality. It's useful to understand what this really means.
From where you are right now, you may see a room or buildings, fields or hills in the distance. Maybe a river, a sea, clear sky or clouds, maybe the sun, the moon or stars. There is a sense that 'I am here and I see that there'. You may hear sounds. Maybe cars, people talking, birds singing, or an aeroplane flying overhead. There is the sense that 'I hear sounds'. These perhaps are the main two senses, but there are other senses where we may feel that 'I experience that' - maybe a taste or the texture of clothing. It's the world of perceptions, and we have the sense that 'I am perceiving this'.
As well as the usual senses, we also perceive thoughts. Sometimes it seems that thoughts 'have a mind of their own'. They ramble on from one topic to the next. Other times it seems that we are intentionally thinking about something, like planning an event, deciding what we need to buy or say, or thinking about something that interests us. Either way we feel that 'I am thinking thoughts'.
We also experience emotions, such as sadness and anger, joy and relief. There is a sense that 'I am happy' or 'I am sad'. We feel sensations like aches and pains. There is a sense that 'I have a headache', for example. But in Non-Duality we like to know what is happening here more clearly. We like to know who is this 'I' that experiences these perceptions, sensations and feelings. Who am I?
From the Non-Duality understanding, we are not what we can see. The eye cannot see the eye, and I cannot perceive I. In everyday life we talk of 'I' as if I am a human being. But in Non-Duality there is no true limitation of any form. The human body has no true beginnings or ends by which it can be accurately defined. That's not who we really are. All that we can say for sure is that I know I exist. I see the body and the world. I hear sound and feel pain. I notice thoughts and thinking.
In Non-Duality we are the Witnessing of all perception, feeling and sensation. Some call it Awareness or Consciousness. We are Knowing. Saying we are 'The Witness' is less accurate than 'Witnessing', as 'The Witness' implies an identity. Identity requires definition and limitation, but Reality is limitless.
So there is a practice of 'Witnessing', or 'Being the Witness' if that feels more comfortable. It means not identifying with what is perceived and not getting caught up in the experience. It's observing the mind, the body and the world, witnessing thoughts, perceptions and sensations, without attachment to them. This is more in line with limitless reality than 'I am this form and I do these actions'. What is perceived is not the perceiver. Actions that are done are not done by the perceiver, they are witnessed.
This practice of 'Witnessing' is the untangling of attachment with forms. Moving from the sense of 'I am sad' or even 'I am happy', 'I am well' or 'I am in pain', to the witnessing of the feelings of sadness or joy, wellness or pain, without identification with them. The one who witnesses is not what is witnessed. This practice is about recognising that our permanent unseen presence is not something that is observed in the world of changing forms. Our permanent unseen presence is where we are perceiving from.
Seemingly paradoxically, to remove the false identification with limited form, we need to separate ourself from this. We need to step back and see that we are not a separate limited form. However, it is to be further recognised then that this world of changing form is not separate from who we are. All form, thoughts, humans, animals, buildings, mountains, rivers, planets, stars, appear in the Consciousness that we are. The error is in the belief that we are a limited form that comes and goes. The Reality is that we are timelessly Here. We are Unlimited Formless Consciousness and all forms appear in Consciousness, made of Consciousness, known by Consciousness.