You raise a lot of questions, and I will go about them one by one, hoping you won’t mind.

1). Everything is a belief until the belief is replaced by a conviction based on an experience – or experience-knowledge – , the experience (intuition + reasoning) needing no proof.

2). Consciousness and intelligence are prerequisites for understanding what any concept (e.g. ‘matter’) means. Without consciousness, nil. That is why it is logically, ontologically, and epistemologically prior to any enquiry or investigation. Can this be contested?

3). When writing or reading, are you and I conscious? Is there need of a proof for this (which I call reality or fact)? The fact of being conscious as a living being is irrefutable. Another question is whether it is the brain, or consciousness/mind, that which is causal in this ‘binomius’ – subject-object (thinker-thought).

4). Descartes posited an ‘I’ (cogito) invalidly – instead of saying: ‘a thought/thinking is happening’, as his first premise, he posited the subject, ‘I think’ (cogito) – but he was not entirely amiss when he went on to distinguish between ‘res extensa’ and ‘res cogitans’ (which is refuted by non-dualists as well as by Berkeley). The problem here, extensive to most of Western philosophy, is conflating mind and consciousness. For Advaita Vedanta (from now on AV) mind is an object of/for consciousness which, together with all that it thinks of, appears and disappears (e.g., swoon, deep sleep, etc.). Not so consciousness, which is invariant and ever present. Thus, objectless consciousness is a fact, not a theory.

5). So, the idea that the “‘I’ of Descartes has been clearly shown by both science and philosophical/religious schools to be a creation in the brain with no concrete reality”might be true if one takes mind as including, or replacing, consciousness. If, on the other hand, ‘consciousness’ is substituted for ‘mind’, then religion, philosophy, and many scientists (those who do not buy into physicalism, a particular doctrine or belief) will not raise that objection, as suggested by point #4.

6). Non-duality, including Advaita (a-dvaita, not two) is not exactly the same as Monism. Who says that “advaita, = not two, is usually reduced to ‘oneness’, which is another form of Monism”? I am aware of that confusion. The non-dualism of AV signifies that Atman (true Self) and Brahman (non-dual reality) are not two numerically different entities, but rather two (epistemological) aspects of one and the same reality – thus removing any ambiguity. The same can be said about the bipolar concepts ‘subject-object’). Clearly, then, I beg to differ from the Indian scholar you mention (“[Advaita] should be called Monism rather than Non-dualism”).

7). Contrary to what you say Buddhists postulate either emptiness/void or dharmakaya as the ultimate reality or truth – or what can be called such. That tradition is different from AV, but the experience (if such an experience happens) comes to the same thing: ineffable oneness. (BTW Oneness is not monism; it is other than what you stated above: #6).

8). You: “There is simply no way to separate consciousness from phenomena. Science cannot do it, and the philosophical or religious mind can’t do it”.

My reply: (Understanding) AV does it: Objectless consciousness is a fact and a possibility of experience (#4). Since Brahman is the only reality, there is no possibility for ‘any thing’ to be objectified as seen (contemplated) from paramarthika (again, ‘not-two’).Thereby mind becomes no-mind, as it were.