Ben
"because you've defined your position to be unfalsifiable"
Exactly. Because it is. Because we must start somewhere. Because it is determined by how we (and all sentient organisms) detect 'existence', and how that form of existence (ie what is potentially detectable) must occur (ie our physical existence-there may or may not be other forms, but we cannot know them, any judgement on any other form than the one we can know is just belief/speculation, even if it 'appears' scientific). Existentially, we are locked into what we must assume logically to be only one particular form of existence. But we cannot transcend it.
Put simply: I can assert that our physical existence is a 'shoot em up' game being played by green giants with six heads. That is a statement that alludes to something extrinsic to our physical existence. So it is useless scientifically, because it cannot be known. If we came into contact with an alien, then, by definition, he/she is no longer an alien, but is part of our physical existence, just not human. Similarly, if we detect some phenomenon which does not accord with proven assumptions, then we can hypothesise about some other phenomenon causing it, even though we cannot sense it. The difference is between what is provable on the basis of validated direct experience, and/or hypothesis properly derived therefrom, and what is not provable on that basis (not that we will always get it correct in practice, but that is the principle).
Now, the question then becomes: how can this form of existence occur? Drop the notion of 'universal frame'. Forget all about observation, or indeed any form of sensing. Because that form of existence occurs independently of sensing. Furthermore, it involves alteration. Why? Because sentient organisms receive physical phenomena when sensing, ie something exists 'out there'. And when inputs are compared, differences are revealed. So the existent something out there is altering. That means our physical existence is existential sequence. And the key feature of that is that only one physically existent state of it can exist at any given time, because the predecessor must cease to exist so that the successor can exist.
Put simply: our physical existence is like a 'what the butler saw machine' (or a movie). Each card representing the entirety of our physical existence at that time. Which must not involve any form of change, because something cannot be in a physically existent state and be altering Ie in another existent state) at the same time. Another way of putting that is, what is it before it alters, and/or what does it alter to? It has got to be in a definitive existent state to be able to alter into another definitive existent state. Anyway(!) rather than one card, the constituent elements on that card, could each be represented on separate cards, ie there is now a lot of these machines (there is a logical problem with that, but for the sake of the analogy-run with it). So, we can either crank the one machine forward, the speed at which we do so being the speed at which physical existence does so (timing measures rate of change). Or we can crank the entire set of machines forward together at that same speed.
The "global sequence assumption/universal frame" is a function of the very nature of the physical existence we are investigating. Not an assumption.
Then, and only then, can we consider the sensing of this physical existence, which is another 'reality', in that it comprises physically existent phenomena, but is not the reality we are trying to investigate. From the perspective of the sensory systems it is a representation of that reality (ie it is light, noise, vibration, etc). These two realities must be differentiated.
Paul
