We can understand the universe, but why? Nobel Prize-winning physicist and mathematician Eugene Wigner said in 1960, “The enormous usefulness of mathematics in the natural science is something bordering on the mysterious and there is no rational explanation for it.” Albert Einstein expressed a similar thought: “The most incomprehensible thing about the world is that it is comprehensible.”
What some Christian apologists claim
Many Christians have seized on this, claiming that an understandable universe points to God, both because God would want us to understand it and because only a theistic approach can explain such a universe. World-famous apologist William Lane Craig gave this religious interpretation:

It was very evident to me that [naturalists are not] able to provide any sort of an explanation of mathematics’ applicability to the physical world, and this was self-confessed…. Theism [enjoys] a considerable advantage in [being able to answer this question].

Philosopher Nicholas Maxwell added:

Why should the physical universe, utterly foreign to the human mind, nevertheless be comprehensible to the human mind? We have here, it seems, an utterly inexplicable link between the physical universe and the human world…. Of course if God exists, the comprehensibility of the universe is entirely understandable.

Let me push back a little. These interpretations make a huge, unstated assumption that a godless universe could not look like our universe, but what supports this? Do they think that the dependability of physics is only due to God? Do they think that a godless universe would it be unstable, with constants, exponents, and relationships continuously changing? Perhaps in this universe, e = mc² would be valid one moment but then e = mc^2.1 the next and e = 17mc^3.5 the next?
That our physics wouldn’t look like it does without God is a very bold claim, for which I see no evidence. Furthermore, “God did it” is unfalsifiable, which is a fatal trait for any theory, let alone one that claims to explain all of science’s most perplexing problems.  (I give a more thorough analysis here.)
Hold on—is the universe understandable?
Let’s reconsider the initial claim, that the universe is understandable. Sure, we can find simple relationships between aspects of reality with scientific laws such as PV = nRT, V = IR, F = Gm₁m₂/r², and so on, but things become more complicated. Corrections for relativity must be added to Newton’s Law of Gravity (F = Gm₁m₂/r²). Ohm’s Law (V = IR) ignores capacitance and inductance, which makes calculations of time-varying voltage or current much more complicated. And the Ideal Gas Law (PV = nRT) makes assumptions about gases that limit its applicability.
The universe is understandable? More precisely, what we understand about the universe is understandable, which isn’t much help in anticipating how science will continue to progress as we push the frontiers. How much about the universe will we eventually understand?

Knowledge about the universe can be divided into four categories, as illustrated by the Venn diagram above.

1. What we know. This has expanded dramatically since the modern period of scientific discovery beginning around 1800, which includes scientists such as Maxwell, Mendeleev, and Tesla, and even more so since the Enlightenment period, which might include Galileo, Newton, and Pascal. Imagine how small the “What we know” ellipse was 500 years ago.
2. What we will know. No one knows if we’ll continue learning about the universe at the current rate, but it seems a safe bet that we’ll know much more a thousand years in the future (assuming human society stays safe).
3. What we’re capable of knowing. What more could we understand if we only asked the right questions or if super-smart aliens taught it to us? Theoretical physics, like science fiction, can only take us to places that its practitioners can dream up.
   Another limit is our finite ability to create technology. To satisfy Big Physics, engineers have built the Large Hadron Collider, the Laser Interferometry Gravity Observatory, and the Hubble Space Telescope, and they’re planning next generation versions. But what if we eventually needed versions that were a thousand times bigger or more expensive? Or a billion times? Human society, even far into the future, might have limits. Without these monster machines, doors to unimaginable truths might remain closed.
4. All foundational knowledge of reality. The final ellipse is everything—not trivial specifics like the atmospheric composition of Alpha Centauri’s fourth planet but every concept, law, and theory needed to describe life, the universe, and everything.
   Our imperfect brains have limits. Imagine an alien species that is smarter than we are to the same extent that we are smarter than chimpanzees. While we share a common ancestor with chimps from just six million years ago, we can find in chimps only the rudiments of higher-order intelligence such as humor, problem solving, and morality. Chimpanzees are our closest living animal relative, but human children surpass their intelligence at perhaps three years of age. These aliens would intellectually be to us what we are to chimps. If chimps can never understand algebra or geometry, let alone calculus or quantum physics, what would these aliens be able to understand that we could never hope to learn? And if chimps will never understand all the science behind reality, why do we think we will?
   Now take it a step further and make the aliens’ cognitive gap the same as between us and lizards. Our understanding the new science these aliens could teach us might be as unlikely as a lizard understanding a joke.

A pessimistic look at our understanding of reality
The figure above gives one version of what we know (and will know) compared to what we won’t, but that’s just an optimistic guess. Imagine if the four ellipses actually look like this:

With this interpretation, we will still make a lot of progress from what we now know to what we will eventually know, but this more pessimistic version imagines the overwhelming majority of science out of our reach, either because imagination or lack of data let us down (third ellipse) or because it is beyond our cognitive reach (fourth ellipse). Will humans eventually understand 99 percent of the science behind reality? Or 0.1 percent?
Most frustrating, we can never know how big the third and fourth ellipses are! We can never understand the size of our ignorance. We will always perceive only ellipse #1, never sure if we’ve learned most of the science or a tiny fraction, never sure if we will learn much more or if we’re near our inherent limit.

See also: The Argument from Mathematics Doesn’t Add Up to God

Let’s return to our marvelously understandable universe. The universe is indeed understandable … but only to the extent that we can understand it. And how far is that? No one will ever know. “The universe is understandable” is an empty statement.
If Christians want to find proof of God in there somewhere, they must imagine a God who tantalizes us with some bits that are understandable, makes us work very hard to understand more, and refuses to tell us just how much of this mess we will ever understand. Doesn’t sound like a proof of anything to me.

The classic theist dodge
is to declare that God answers all prayers,
but the answer can be “Yes,” “No,” or “Wait.”
This means God has fewer options available to him
than my Magic 8 Ball.
— commenter Kevin K

Image credit: Olga Reznik, flickr, CC

In the beginning … God walked in the Garden of Eden like an ordinary supernatural Joe. He dropped by Abraham’s for a cup of coffee and a chat. He didn’t know what was up in Sodom and Gomorrah and had to send out angelic scouts for reconnaissance: “The outcry against Sodom and Gomorrah is so great and their sin so grievous that I will go down and see if what they have done is as bad as the outcry that has reached me” (Gen. 18:20–21).
But, like Stalin gradually collecting titles, God has now become omniscient and omnipotent. He’s gone from needing six days to shape a world from Play-Doh and sprinkle tiny stars in the dome of heaven to creating 100 billion galaxies, each with 100 billion stars.
That’s 6,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 kg of universe.
And yet, oddly, his biblical demonstrations of power faded with time. From creating the universe, he’s weakened such that appearing in a grilled cheese sandwich is about as much as he can pull off today. He has the fiery reputation of the Wizard of Oz but is now just the man behind the curtain.
Even God’s punishments became wimpier. A global flood, with millions dead is pretty badass. Personally smiting Sodom and Gomorrah is impressive, though that’s a big step down in magnitude.
And it’s downhill from there—God simply orders the destruction of Canaanite cities, and to punish Israel and Judah, he allows Assyria and then Babylon to invade. As Jesus, he doesn’t kick much more butt than cursing a fig tree, and today he simply stands by to let bad things happen.
Maybe God’s power diminishes as the universe’s dark energy increases?
Photo credit: Why There is no God