How do we understand the ultimate nature of the cosmos? Via astrophysics? Astronomy? No, scientific disciplines simply assume the cosmos. But they assume it for religious reasons, in that they assume the cosmos of the Bible, not, say, Buddhist cosmology, in which, according to Prof. Wiki,
there is no ultimate beginning nor final end to the universe. It considers all existence as eternal, and believes there is no creator god.
Or Mormon cosmology, in which
The Earth's creation... was not ex nihilo, but organized from existing matter. The faith teaches that this earth is just one of many inhabited worlds, and that there are many governing heavenly bodies, including a planet or star Kolob which is said to be nearest the throne of God.
In short, "Though we are led to think that the universe is the province of a special science," the cosmos "is an irreducibly metaphysical and theological idea" which we only subsequently investigate via scientific methodology.
Moreover, the transcendent unity of the cosmos "is most fundamentally a unity of being" (Hanby). It really is One Thing, not an agglomeration of units, "each separated by an ontological abyss from each other."
"[I]f the cosmos is not inherently intelligible, if its logos is not intrinsic to it," then knowledge and truth become "impossible by definition.... The very possibility of cosmological truth depends upon reality being intelligible 'all the way down (and up)'" (ibid.).
A key point is that scientific knowledge -- in fact, any knowledge -- follows from this principle of the unity of being. Put conversely, if not for the prior unity of being, no knowledge of any kind would be possible.
But a cosmos lacking in oneness is an absurd proposition, because in a fundamentally fragmented and dis-unified "cosmos," there couldn't be any organic unity, and therefore no organisms or knowers. (I put cosmos in scare quotes because there couldn't be one; rather, each atomistic monad would be its own enclosed world, as it were; this would be a multiverse of exteriorly related billiard balls.)
Speaking of unity of being, did you know that cosmos, cosmetology, and cosmetics are related? The term kosmos
denotes order and beauty, even more specifically the beauty resulting from order, the beauty that is still implied today by an activity that derives its name from the word -- cosmetics (ibid.).
So now we see that both order and beauty are built into the cosmos. Why are we surrounded by such beauty? Because of a unity of being that at once gives rise to truth, beauty, and goodness (or the moral law). "Cosmology and anthropology are always correlative" (ibid.).
Not only are they correlative, but of the two, anthropos is ontologically prior. You might say that it is with God from the beginning. In other words, while they are complementary, the cosmos ultimately derives from the person(s) in whose image we are.
In this context, what we call causation is itself "a communication of meaning" (ibid.). Science is only possible because of our communion with being; or science is a communion that takes place between between subject and objects that are unified in being. Knowledge is a reflection of being, as immanence is a reflection of transcendence, or infinitude of absolute: I AM, therefore we can think.
For Schuon, "the laws of intelligence... reflect the laws of the divine Intellect." The Intellect is a prolongation of the Absolute, which is why reason "prolongs the Intellect in the direction of relativity." In other words, man always faces in two directions, up and down. But you cannot derive up from down!
So yes, man can understand the physical cosmos. But "one cannot understand the world unless one understands the place of understanding within it" (Jonathan Lear, in Hanby). In other words, it makes no sense to understand the cosmos while failing to understand how and why you can understand it, or worse, positing a cosmos that cannot account for its own capacity to be understood.