Marcoen
"The sentence "we cannot know what we cannot know" is a tautology, and of little value".
Not so. It is a fact, and lies at the core of properly differentiating what we can investigate, from what we cannot, scientifically. A mistake philosophers usually make from the outset. Whatever physical existence is, we can only concern ourselves with the form of it (there may or may not be another) which is manifest to us, ie what is potentially knowable (which includes both directly validated knowledge, and hypothesis in the form of virtual sensing). Knowing being determined by a physical process, not philosophical ideas.
"Kant however..."
This is an example of how people get it wrong, but it sounds good. What is in our heads is irrelevant. That is, obviously, a perception of reality, not reality. Nobody, except those who do not understand how physical existence occurs, attributes processing in the head with having any affect on the physical circumstance, because that processing is not a physical process, and more importantly, the physical circumstance has already occurred, which is why it can THEN be processed in the head. Physical existence, for us, comprises an existential sequence and existent representations thereof (eg light). "Kant then stated that we cannot know the latter by observation." Which is incorrect, because as I stated above, it is critical to differentiate what is knowable from what is not. And, also, to understand that observation, or any form of sensing, revolves around the receipt of a physical input, this being the determinant of the form of existence we can know. The subsequent processing thereof being of no consequence to the physical circumstance. Within the existentially closed system of existence as knowable to us, it is possible to discern what occurred from the physical input received in any given sensory system (it may prove in practice to be impossible, but it is possible). That there might be an alternative to this is irrelevant, since we cannot, even potentially, know it, ie it is the impossible.
The overall point is that existence is independent of the mechanisms which enable awareness of it. Those mechanisms only enable one possible form of detection. But that is all we have, we cannot externalise ourselves from our own existence. So as I said, science can only be concerned with what is potentially knowable to us, not possible alternatives which, by definition, we cannot know. Religion does that.
A contributor to this site (Ray Monroe), who sadly died, introduced me to that book. Needless to say I was not impressed. Having established at the basic generic level how we are aware of existence and how that must occur, and then identifying why therefore relativity, spacetime and QM are fundamentally flawed, I have no desire to go any further. I am now finding the whole topic boring.
Re point 1. See above.
Re point 2. Just how, precisely, does one "disturb the microsystem" when one "measures" it? What is being measured must have already occurred. And whilst that fact kills this ludicrous concept stone dead, a further consideration is that the physical interaction involves an existent representation of what occurred anyway, it is known as light. Observation involves the receipt of light, which itself was generated as the result of a physical interaction with what occurred. What this, and other, flawed ideas are really about is an attempt to rationalise the fundamental problem with these theories, which stems from an incorrect presumption about how physical existence occurs. They presume some form of indefiniteness. Which is incorrect. But having made that mistake, there is then a constant battle to keep the theory 'on track', as physical existence occurs in a definite physical state. It should also be noted that no form of experimentation could differentiate discrete physically existent states anyway. The degree of alteration and duration involved is vanishingly small, apart from the fact that we are reliant on the ability of light to represent it. So this is not a method which can be utilised to substantiate a contrary presumption as to how physical existence occurs.
Paul