What can be logically prior, what must be assumed, what is the metaphysically necessary apriori starting point? Here I present the one necessary before I can focus on understanding time in order to derive Einstein locality. These are crucial steps in rendering quantum mechanics naturally expected,[1,2] which is the only interesting aim, because Einstein’s relativity alone easily emerges from classical substrates, while the apparent non-locality of quantum mechanics cannot; well, except via brain-in-vat/The Matrix scenarios, but that just underlines how quantum mechanics indeed relates directly to the apriori conditions of phenomena.
‘Fundamental’ physics needs a ‘Kantian’ approach enlightened through Ludwig Wittgenstein. Language is crucial! Niels Bohr and John Archibald Wheeler understood that fundamental physics is about what we can say, but they still succumbed to the urge to add ‘not about what is’, much like the early Wittgenstein. The later Wittgenstein grasped the importance of the inevitable implicit re-defining of “what is”.
‘Quantum mechanics promotes the mere "observer of reality" to the "participator in the defining of reality." It demolishes the view that the universe exists out there.’ Wheeler 
Participating in the “defining of reality” is good, but Wheeler fails (!), because whether “the universe exists out there” depends precisely on defining “universe” and “exist”.
E. W. Mielke (left) with J. A. Wheeler, 1985, Kiel, GermanyI desire to refuse inflation of verification transcendent distinctions about what is “ontological versus epistemic in metaphysics”. I desire to refuse the naïve-realistic mindset about whether, for example, probability and time “really exist”, spastic self-destructions of terminology. However, all a ‘postmodern’ approach can do is to supply an alternative, because meaningless words cannot be targeted properly without giving them meaning while doing so, thus one usually ends up being wrong when refusing something. The indescribable is precisely that – indescribable!
Many sentences must be read several times for the reason alone that they can be rewritten in different, seemingly clearer versions in order to become wrong in different ways, which is how we extract their relevance for what, in Wittgenstein’s words, cannot be talked about (clearly).
1.1) This is a start (1.1). The start is always the start, and so, the ‘ultimate’ description of everything has several reasons to start focusing on it, because the ultimate description (in some sense must be assumed to have) ‘resulted’ from reasoning processes about the question of what issue can be started with (what is ‘prior’) in order to be able to describe consistently and satisfactorily (without leaving out the very questions we are after): Should the pre-assumed be, for example E1), some mindful attention to the intended or intensional, or example E2), the thus to some degree anyway pre-assumed “physical”, a ‘substance’ conserved through an in some sense ‘absolute*’ time that on some level must be assumed by the mere fact of that histories have causality (else we refuse to call them “history”)? Here it is neither, but instead example E3), namely self-referential description is ‘prior’. (As alluded to in the introduction, I do not refuse the ultimately unsatisfying E1 and E2.)
* [The absolute is always relative to what makes the absolute/relative distinction meaningful in the given context. The only “absolutely absolute” is the implied ‘absoluteness’ (a feeling). Whether this goes one level ‘up’ or merely inflates language by one more word that makes people feel whatever way, is relative to measures that may render “up” meaningful. If you do not like how I handle this issue, try Category theory instead – good luck.]
1.2) The limits on ‘language games’ (“language games” in the widest sense, perhaps wider even than Wittgenstein and Wilfrid Sellars meant) logically relate to the limits on description. The start (1.1) is one such limit. You just crossed that limit to enter this description, or perhaps you started reading from here, so the start of the description is not an “ultimate” limit. However, the start can neither be crossed (in a restricted sense) nor avoided by the description itself, and in that sense, it is already an example for an ultimate limit of the description! The exercising of self-referentiality here has made you find yourself with(in) a description that describes itself, its own limits. It does little else yet and is in that sense vacuous. However, this ‘tautological emptiness’ is the desired absence of assumptions; assumptions may sneak the desired conclusions in through the backdoor. The description relates generally to limits of all those descriptions that suffer from self-reference that at once must be assumed and on the other hand seems impossible: The theory of everything (ToE), the ultimate foundation of physics, which must include understanding “time” and the unification of the two event-structure relativities, namely Einstein’s and Everett’s, “causality”, and general description-relativity (see Postmodern Physics), including the duality transformations between theories, like super-stringtheory (SST)-dualities of the Maldacena type (gravity ~ gauge theory in different number of space-time dimensions), which has shown general relativity to be describable as emergent in a way that does not suffer from the drawbacks of Einstein-ethers.
“The limits of my language mean the limits of my world.” Wittgenstein
‘My’ description of the universe’s ‘reality’ defines “my world”. Fundamental limits on ‘language’ are universal limits.
1.3) I desire to present a ‘fundamental’ description. “Fundamental” means ‘irreducible’ and ‘comprehensive’ as in “not excluding anything important”. “Reducible” and “fundamental” are often misunderstood [in detail discussed here] as something somehow smaller (e.g. spatial resolution) or non-composite. However, what is reduced to what else, that is relative to the description. Duality transformations between different descriptions can leave the one or the other being more ‘fundamental’ or composite in “essential ways” - the Maldacena duality is a good example. So what do I mean by “fundamental”? Note that the term “fundamental physics”, say currently on wikipedia, is taken hostage by particle physicists promoting their own field as the fundamental physics. That is a possible choice of language! Nevertheless, for me, the ‘fundamental’ description must ‘explain’ the presented fundament as naturally expected, or describe satisfactorily why we cannot go further; why the fundamental end is indeed implicitly reached; and how other versions are dual to what is presented. Otherwise, I would admit not to give a fundamental description, but rather, for example, some narrow subfield of physics.
1.4) The fundamental description (“in any universe, for any observer/describer” if terms are suitably defined) is constrained by several aspects, which I do neither thus claim to be “fundamentally different” aspects, nor to be not the same as “fundamental physical law”: I) It Being a description, a ‘language game’ in the widest sense [including ‘language games’ being constitutive for conscious observation as a ‘collective effect’ inside any “physical” description, say involving a brain]. II) Having to be consistent with (describing or the ‘existence’ of) itself. III) Describing something else, while in some sense, description as such never goes beyond itself. IV) It must describe the phenomena and thus presupposes them in some way while it may not naively presuppose them.
1.5) Thus, I take as prior only and precisely what no fundamental description can do without: Itself; the apriori constraints on there being a “fundamental (self-)describing” in some sense at all! Whether there “exist” “universes” “without” “describers” but “describers” “without” “universes” cannot “exist”, such depends on the description, for example on how “exist” is constructed and used.
1.6) A bare ‘reality’ (without mental/physical distinction) or domain is implied by that different, and thus multiple, ‘alternatives’ that are somehow mutually correlated, are presupposed by any description. Self-description alone presupposes multiplicity of the described, that the described is, via the description, a multiplicity of alternatives that are at once different relative to some distinction while being fundamentally equivalent, the difference being irrelevant in some fundamental perspective. This is all the ‘many worlds’ necessary.
OK - I need to explain this more carefully or it seems ad hoc, so let me add some and also 1.7, and then 1.6) above should be much clearer:
You may be interested in how our universe can produce a fundamental physics theory describing that universe, or be interested in consciousness as self-report; regardless: Self-description presupposes multiplicity (differences) of the fundamentally equivalent (no difference), via the aspect of describing (somehow ongoing or completed, that is irrelevant) implying the division of the description, the focusing on different parts of itself in thus different parts of itself. There are different yet (via the description) correlated “states of attention” of the description. Description cannot describe (assume or result in) there being only one alternative to be described 'in totality', there being only one incarnation of a describer, it being only one part. I focus on this carefully in such a way as to not assume space-time or mind or randomness. Those should be derived if possible.
1.7) All 1.6) basically does is saying that multiplicity via difference implying equivalence (on the basis of which the distinction can relate different parts by distinguishing them in the first place) is apriori, however, I do it via what I suggest for now to call the “Different Alternatives that are Fundamentally Equivalent - core concept”, because in this format, it allows me to easily derive different conclusions when the concept is applied to different issues, as I will describe in detail with the issue of time/causality next month [link to be updated]. For now, mainly as an exercise in order to make the "DATAFE"-core-concept better understood, let me remind of the issue of uncertainty, also because it relates directly to quantum probability (as perhaps better argued here and in [1,2] of course).
Self-description has different parts that differ through focusing on (combinations of) different parts. The equivalence between the parts implies an uncertainty: It does not matter whether this part or another one focuses on “uncertainty”, and thus it is uncertain, because the alternatives are equivalent; doing it this or that way is deeply irrelevant to the description. And so we have always “uncertainty”, correlated “alternatives” of self-describers finding themselves (in one or another alternative, which alternative, that is uncertain relative to, for example, the past) describing themselves, and we have also those alternatives’ fundamental equivalence as belonging to fundamental description by definition. It would simply not be a fundamental description without. The nature of the uncertainty lies inside the description, for example the self-identification of different parts. I write “this” and I write “that”; which one should I write first? They are different, yet equivalent. If I construct a difference relevant to this description, I may prefer one over the other, but here the description wants to focus on the equivalence. So how come I wrote first “this” and then “that”?
Well, “I” didn’t! Only if “I” self-identify with this alternative while refusing to include the alternative ‘me’ under the label “I”, only then is the alternative where “that” was written in place of “this” not ‘me’. Fundamentally, they are equivalent. I have not constructed a world with a fair coin to toss; all I have is fundamentally equivalent alternatives of a describer (the description) finding herself describing (herself). Now add that the very core of quantum probability, what makes that core 'quantum', is that quantum statistical correlation is incompatible with ‘absolute actualization’ of futures[1,7]. Thus, that core belongs to fundamental description by definition. If your description does not have it, your description is not yet as fundamental as my description; it misses to include something fundamentally equivalent.
I introduced the ‘Different Alternatives that are Fundamentally Equivalent’-core concept of tautological modal realism (TMR), which is the self-implied domain of fundamental theorizing (totality of all that is describable). This core concept will imply relative simultaneity and thus Einstein locality in emergent space in the next part [link to be updated].
 First suggested in: S. Vongehr: “Realism escaping Wittgenstein’s Silence: The Paradigm Shift that renders Quantum Mechanics Natural”. 4th FQXiEssay Contest http://fqxi.org/community/forum/topic/1483 (2012)
 S. Vongehr: “Historical Parallels between, and Modal Realism underlying Einstein and Everett Relativities.”arxiv:1301.1972 [quant-ph] (2013); Popper’s proof  of future indeterminism is turned upside down (also here) in order to shatter the past already (not the future) into many worlds/minds. As a result, quantum mechanics turns out to be the Bell inequality violating correlation between those possible pasts, but basic Everett relativity as relative actualization between those pasts is anyways prior.
 K. Popper: “The Open Universe: An Argument for Indeterminism.” Roman and Littlefield, Lanham, MD (1956)
 This work also mine, but there are plenty of references of more established people in this work that prove the point: S. Vongehr: Supporting abstract relational space-time as fundamental without doctrinism against emergence. arXiv:0912.3069 (2009) arXiv:0912.3069
 J. A. Wheeler: “The Quantum and the Universe in Relativity, Quanta and Cosmology II.”, M. Pantaleo and F. de Finis, eds. Johnson Reprint Corp., New York, (1979)
 L. Wittgenstein: “Tractatus Logico-Philosophicus.” Routledge and Kegan Paul, London (1922) This text explains spreading of actualization via a intuitive model but I admit the text is horrible and needs a revision very badly (Give me until October): S. Vongehr: “Many Worlds Model resolving the Einstein Podolsky Rosen Paradox via a Direct Realism to Modal Realism Transition that preserves Einstein Locality.” arxiv:1108.1674v1 [quant-ph]