Question: Since for my [last question](https://buddhism.stackexchange.com/q/47334/16806), I did not get a satisfactory answer I am reducing the question to its barebones.

What is the difference between 'Witnessing' and 'Mindfulness' from the context of meditation? I mean when I am looking at the sunset without any thoughts in mind and feel a oneness, am I witnessing the sunset or I am being mindful of the eye-consciousness?

In the [Mahāsatipaṭṭhānasutta MN 10](https://suttacentral.net/mn10/en/sujato?layout=plain&reference=none&notes=asterisk&highlight=false&script=latin#mn10:2.1) the word mindfulness is used, can I replace it with the word, 'Witnessing' without changing the meaning?

Answer: 
sati ("mindfulness") is one of the most commonly misunderstood teachings.
It's been distorted by psychotherapy agendas, and even experienced Buddhist teachers have wildly divergent understandings.

If you want the perspective from the original suttas:
There's an implicit object of sati, and that's the Dharma, the Buddha's teaching that leads to nirvana.
One always remembers to apply the Dharma. All the time.
The fourth frame of sati, seeing Dharma as Dharma, is commonly misunderstood to be seeing thoughts (the dhamma that the mind/mano cognizes/viññāna).
But the primary role of seeing Dharma as Dharma, is living each moment in accordance with the Buddha's Dharma, and the dhamma-thoughts cognized by the mind are subservient to that primary objective.

More detail here:
<http://notesonthedhamma.blogspot.com/2022/12/two-ways-in-which-sati-mindfulness-is.html>
Maybe see the Quora thread on Osho's "witness": <https://www.quora.com/What-is-witness-meditation-as-described-by-Osho>

I can only tell from my personal experience: I've read books where "witnessing" was used synonymously with perceiving with mindfullness (sati) and without follow-up thoughts (<https://en.wikipedia.org/wiki/Conceptual_proliferation>)

Your sunset example seems to be a mix of different elements: The basic perception process goes from the object (external) to the eye sense organ to perception to sign (nimitta), but then stopping there (if you are right that there is no mental proliferation).

The feeling of oneness seems to be a separate, second perception from your "internal sense organ". However, it's unclear if the source of this feeling is directly the eye-consciousness, if it is mediated by the perception of "beauty", or if it's the result of a separate associative process based on the memories of what Osho told you about oneness.

You may also have a look at oneness and it's background: <https://en.wikipedia.org/wiki/Nondualism>
However, attaining advaita usually takes years of meditation practice. Perception of beauty is said (by Sangharakshita somewhere) to provide a glimpse of it.