Good OP! But are you sure “intelligible” has to be about human reason?
I don’t find it objectionable to say that something can be intelligible to a better/stronger/different reason than ours. After all, molecular structure is intelligible – but not to my cat. There could be an infinite number of phenomena in the universe that are similarly beyond human understanding, but not therefore unintelligible.
Because the universe is not intelligible to us we cannot say whether or not the universe is intelligible.
There are some phenomena which are not currrently understood. That does not put them beyond understanding.
There is an interesting J.L. Borges story about an object called the Zahir. As far as I remember it, it appears as many things for people (a tiger, a blind man, an astrolabe), and it kind of represents deep fascination toward one’s object of focus, as a kind of mystical absorption, which parallels a wonder of the whole. The aspects of a thing which, by the open possibility of comparisons, seems unending. It plays with the theme of infinity by borrowing from Borges’ adjacent stories (the Aleph, The Library of Babylon).
No thing appears outside of the contextual web of its conditional relations. We can close in, simplify, abstract, but the thing in itself is too full, in relation and potential to the world by which it receives its meaning.
Think of a the concept of a tree (its peculiar connections in your personal brain). You might require to the rest of the world define it. The more background information lost, the more meaning the tree may lose.
Simplification to the abstract, to cut away in focus, makes things intelligible but there is always a sense for persists outside of that, the potential of projecting unnecessary meanings, the lack that aches us to do the work of understanding, which recyles like any other periodicity of nature. Our desire to know in some sense is a kind of affliction because we are never content to end in the meditation of any thing.
Perhaps the question of why there is anything at all rather than nothing, characterizes this excessive feeling of wanting to know what is unknowable. Even if we were gifted an answer we wouldn’t be satisfied.
But maybe this has nothing to do with the question.
The universe is at the same time intelligible, but that mode of abstraction reduces it into something much less than it is, a part/representation that can be grasped/viewed, but remains fuzzy is its (in)exhaustible potentiality.
Plato believed that physical reality reflects deeper truths beyond our senses, while Kant argued that we can never fully know reality as it exists in itself. Therefore, the universe is not be entirely intelligible to the human mind, even if we can understand parts of it.
We’re on the same page. A linguistic mishap on my part.
Would you say that QM is unintelligible? Take Schrodinger’s cat and the insistence of people like Einstein that there’s got to be hidden variables. Shut up and calculate ~ N. David Mermin (on the Copenhagen interpretation) speaks to how QM is weird and unlike (say) gravity.
There’s a deep irony in asking if the universe is intelligible on an international forum using a small gadget probably manufactured on the other side of the world.
It’s a fascinating question. What does it mean to say that the universe is intelligible?
Is rational order something we discover in the universe, or does it have more to do with how our cognitive apparatus is configured? Perhaps we don’t so much see the universe as it is as organise our experience in ways that make it intelligible to us, using concepts and descriptions that prove pragmatically useful.
Personally, I think we have a workable sense of intelligibility that allows us to intervene in the world, make predictions and communicate with one another. But what makes this possible, exactly? And does it tell us anything about reality itself, or only about how we have learned to make sense of it to some extent?
Does the world need to be rationally ordered with “inevitable features” or does it just need to present us with regularities, invariances, recognizable and reliable patterns of things, events and processes, to count as being intelligible?
Why should intelligibility be confined to that which can be understood by human reason? If the question is interpreted more modestly as asking whether environments are intelligible to the animals that inhabit them, then it would seem the answer must be “yes”. An animal must be able to function “sensibly” in its environment, else it could not survive. The human environment is greatly enlarged by language and culture compared, as far as we know, to the environments (worlds, Umwelts) of any of the animals.
Your OP makes it sound as though the Universe does not qualify as intelligible if we cannot discover an"ultimate" or “final” reason for its existence. How could we ever know we had discovered such a thing? The very idea that there could be an overarching reason for the existence of the world invokes a creator. How could we ever know whether there was a creator? What I think we do know is that idea of a creator cannot even be coherently formulated .
The idea of a reason for the existence of the world that lies outside of the world (as it would have to in order to count as a reason for the existence of the world) also seems incoherent to me.
Granting for the sake of the argument that we and the other animals do form models of their environments that enable them to navigate successfully and survive, would you not count those models as examples of sense-making, and thus of intelligibility?
This is a very interesting observation. We create the universe we live in, guided by the rule of “make it make sense.”
Yes, things need to be predictable
Yes, an animal may understand its immediate environment, but as humans we wonder about the entirety of existence.
But, sometimes what makes sense to us is not always an accurate reflection of the way things really are
I think one interesting aspect of intelligibility is that we can discern relations of necessity through reason alone. And isn’t that the very basis of intelligibility? Things that just ‘make sense’?
For instance, if I know that A is larger than B, and that C is larger than A, then I will know that C must be larger than B without actually comparing them. This is a priori knowledge or necessary fact.
But then we can also apply logical and mathematical reasoning to derive predictions about what actually happens, or is what is going to happen. We’re able to connect relations grasped through reason with the behaviour of the world we experience. Mathematics is not itself an empirical observation, yet applied mathematics enables us to predict empirical events with great accuracy. I mean, we’re constantly surrounded by the evidence of that, the device you’re looking at right now being an example.
But on the other hand, there’s a strong tendency in modern culture to question, or at least relativise, the intelligibility of the Universe. The “laws of physics” are nowadays said to only hold “in this universe” (ref). I think the old–fashioned “principle of sufficient reason” — that everything that happens has a reason or cause — is nowadays regarded as unfashionably religious. The zeitgeist is that everything is ultimately contingent, reality ultimately unknowable, but that science can be used to many useful ends from our perspective.
Right, but you haven’t said whether things just need to be predictable in order to count as being intelligible. Also all things are obviously not predictable, or at least completely predictable, things, among others, such as the weather and human behavior.
Is there any entirety of existence? It certainly doesn’t seem to be available to the senses. Is it more than merely an idea?
Yes, we can be mistaken when there are relevant facts we are unaware of. Does that rule out things being intelligible, though?
Is it plausible to think that the way we make sense of the universe could be completely unrelated to how the universe is?
It’s partly Kantian so unoriginal but it’s not that we “create” it as such; there is something there we interpret and shape with our values, cognitive capacity and culture. Making meaning and finding predictable responses seem to be how we orientate ourselves.
He did suggest the theory was incomplete and required more, something like hidden variables, but probably not to the point of ‘got to be’.
What he (and others, EPR) argued for was a definite reality and locality. It was later proven that this is not possible even with hidden variables.
As for the theory being intelligible by humans, yea sure, else it could not be discussed. If by intelligible you mean ‘complete’, then no.
QM is weird
What it isn’t is intuitive, thus being seen as weird by anyone giving significant weight to their intuitions.
Same thing. Humans just have a different designation of ‘entirety of existence’ than does something else, including something perhaps more intelligent than us, and including different humans.
But it isn’t. Rock > Scissors. Scissors > Paper, but it does not follow that Rock > Paper. Something more than pure reason is required in this example of a circularly ordered set rather than a linear ordered set.
Yes the cat is both dead and alive is intelligible. I agree. Schrödinger badly mishandled superposition.
But no. Whether someone will win a particular round of Rock–Paper–Scissors is an entirely different question, involving contingent choices. It has no bearing on my point. The point is that, given the premises that A is larger than B and C is larger than A, the conclusion that C is larger than B follows necessarily, without further observation or actions on anyone’s part. That could never be the case for rock>paper>scissors.
“What did you do to the cat, Erwin? It looks half dead.” ~ Ms Schrodinger.
It’s tough on the cat but so long as we don’t peek the cat learns and adapts to its circumstances. After that it’s smooth sailing. Sic vita est. 
P.S. Do you buy into my claim that Schrödinger mishandled superposition?
I think he intended it as a kind of semi-sarcastic parable intended to drive home the ridiculousness of ‘superposition’. When it was discussed in mathematical terms, few could understand it, so he came up with that idea to illustrate how baffling it was. And then the story got picked up by the press and became part of modern culture. That’s my take. But in reality, decoherence (which had not been developed at the time) accounts for why no macroscopic objects can exist in a state of superposition.
I’ve been discussing QM with others. I’m still not clear on decoherence. Hopefully I’ll get there … someday.
As I stated physics - math = tennis - racquet.
\Psi = a| \uparrow \rangle + b| \downarrow \rangle
Pr(\uparrow) = a^2 and Pr(\downarrow) = b^2 such that a^2 + b^2 = 1
There’s nothing wrong with this per se. The calculations predict in experimentally confirmable ways.