St. Thomas’ famous five ways of knowing of God’s existence through our reason and knowledge of the world are plenty enough for most of us to contemplate. Recently, however, in my professional work I’ve run across yet another way in which Creation gives us at least a hint — perhaps resounding evidence — for a Creator. The technical paper which occasioned these reflections — ably summarized for an educated lay audience, with commentary, here, by a politically conservative, atheist Harvard string theorist — is part of a whole literature in physics concerned with the meaning of Entropy for the direction of the flow of time (known as the “arrow of time”) and what Entropy means for theories of a universe that are purely natural — ie, that posit no supernatural origin of things.

Entropy
To summarize and remind readers, entropy is a physical quality, like temperature, that measures how ordered or disordered a system is. A perfectly cold ice crystal would be a low entropy state, while the steam coming out of a chimney is a higher entropy state. One of the most basic physical facts that we know about our world is that, over time, entropy is inexorably increasing. This is an important fact, called the Second Law of Thermodynamics, and it’s built into all of our intuitions about the world. But it’s a bit of a puzzle to theoretical physicists, because all the laws of nature we’ve found are time reversal invariant — Ie, there doesn’t seem to be any part of the fundamental laws of the world that guarantees that entropy should increase. In particular, if we were to see a film of a mound of broken glass jumping off the floor and assembling itself into a coffee mug, we would immediately conclude that the film was being run backwards. However, there is no law of physics, except for the 2nd Law of Thermodynamics, that guarantees this: no fundamental law excludes the possibility of a bunch of sound and heat spontaneously picking up those glass shards and reassembling them into a ordered state.

The Low Entropy Big Bang
Taking these observations and applying them to a Universal scale, we can thus say that our own Universe must have been in a very much lower entropy state when it began all those billions of years ago than it is now. This is fine for any of us who are glad to have God involved in the whole Universe-creation business, but it is a severe problem for the atheist. Why? Essentially because he, to be consistent, must maintain that the Universe in which we live is in some sense an average one among the possibilities, that it was spontaneously born from some eternally existing prior state, and that it should be a predictable sort of product of such a prior state. But if there is anything we know about the physical world, it is that low entropy states never, ever spontaneously form. And in an eternally existing prior state, there would be an infinite amount of time available for entropy to become maximal — therefore implying that there could never be a low entropy big bang.

Fluctuations and Boltzmann’s Brains
“But what about random fluctuations?!” the desperate atheist physicist replies. “If we have all these endless epochs available to us, shouldn’t we expect there to be random fluctuations wherein low entropy big bangs might spontaneously arise?” This idea nearly works, in that it is possible at least to imagine such a thing being true; but it introduces a new problem, that of the so-called Boltzmann Brains. A Boltzmann brain is a human — or at least self-aware — mind that spontaneously is created through a low-entropy fluctuation in the eternally existing universal prior state. It turns out that, since spontaneous lowerings of entropy have a probability that is proportional to the exponential of the negative of the change in the entropy, there should — in the fluctuation believer’s model of things — be infinitely more randomly emerging self-aware Boltzmann Brains than there are naturally emerging minds like us, that live in low-entropy Big Bang universes. Thus, the naturalist, so wholly committed to being in a typical, unsurprising Universe that requires no special fine-tuning or hand of God, is left with the contradiction that he, by the very fact that he lives in a Universe and isn’t just a mind in a bubble, is a very, very, very special mind indeed.

Lots of clever folks refuse to see this as a final nail in their spurious naturalistic Metaphysics, but it shouldn’t come as much of a surprise to anyone who already knows that God made the world. But it’s still neat to see how cleverly He has arranged the signs and laws of that Universe to point to Him. And to end in a way modeled on St. Thomas: There is, therefore, a being who permitted all things to be ordered at the beginning of time, to which all men give the name of God.