The tradition of formal inquiry declares that among equally valid explanations, the one with the fewer assumptions wins. And the fellow who needs the presumption gets to defend it.
This Parsimony Principle goes back to before Aristotle in the Western Tradition. It has been resurrected many times and often with new names.
[The most recent variant is ‘Occam’s Razor’, very popular with intellectuals who revel in obscure citations and latin inserts: Entia non sunt multiplicanda praeter necessitatem].
The burden of proof rests with the claimant. Especially on one as preposterous as this, the claim to an ‘Independent and Separate Observer, Self, Subject’.
But we shall not quibble. And we shall not whine.
The fundamental presumption of Inquiry is the posited presence of an Observer, Self, Subject separate from, and independent of, the Observed Object of Inquiry.
It is meaningless to talk of ‘Inquiry’ if the Subject is conjoined with the Object of Inquiry. But then, the word ‘Meaning’ itself is predicated on the presence of a ‘Me’ [in English, ‘Meaning’ doesn’t carry meaning if not for me being in the middle it].
How do you ‘Inquire’ for a Separated Subject if the very idea of ‘Inquiry’ presumes a Separated Subject?