For the next part of my series about the ‘metaphysics’ in metaphysical naturalism I will be analyzing how modern scientific theories about cosmology fit in to the naturalist worldview. Since I am not a professional scientist, I will be quoting authorities for all critical information. The purpose of this article is more philosophical than scientific, in that it does not seek to advance a particular scientific theory, but rather to demonstrate how modern cosmological theories align with the definition of metaphysical naturalism discussed earlier in this series. Feedback is welcome from professionals, if any of the scientific discussion below has factual errors or is unclear. I have worked to quote scientific authorities in their own words as much as possible, in order that their theories be represented as close as possible to their own views.
The study of cosmology has a long history (see here), but since around the end of the 20th century scientists have reached a generally cohesive view of what our universe looks like. The observable universe that we live in is a sphere with a radius of about 46 billion lightyears. Beyond that the unobservable universe is much larger, and is still inflating rapidly. Within this observable part of the universe alone there are at least 100 billion galaxies (and possibly 500 billion galaxies in the whole universe), and, if modern observational estimates among astronomers are correct about there being 17 billion Earth-sized planets in our galaxy, then the rest of the universe no doubt contains many, many more.
In the 1920’s American astronomer Edwin P. Hubble discovered that our universe is not static. Instead, space is expanding rapidly. Current estimates calculate the rate of expansion at 74.3 (plus or minus 2.1) kilometers per second per megaparsec (a megaparsec is roughly 3 million light-years). Since, looking towards the future, the universe is expanding out of control, looking towards the past, we would expect the universe to have emerged from a much smaller point.
The modern theory of the Big Bang answers this question. Scientists have traced the expansion of our universe to a very small initial state about 13.82 billion years ago. Before the expansion, our universe, including its matter and radiation, was compressed into a very hot and very dense point of mass just a few millimeters across. This state is theorized to have existed for a fraction of the first second of time, before a massive blast caused the universe’s matter and energy, and even space and time, to expand rapidly. In the trillionth of a trillionth of a second after the Big Bang, the universe expanded at an unfathomable rate from merely the size of a pebble to being of astronomical scale.
This sequence of events has left us with a vexing question: what caused the Big Bang?
The information above about the expansion following the Big Bang represents accepted scientific fact, but, since scientists have not yet reached a consensus about the cause of the Big Bang, the remainder of this discussion will discuss plausible scientific theories about our cosmological origins. These theories are not accepted by all scientists and may be revised or abandoned with time; however, given the present state of the evidence, these theories are advanced among some of the best scientific experts in their field.
Despite the fact that the biblical account in Genesis 1 describes a world that was created in 6 days, with the sun, moon, and stars being created on the 4th day, in the face of our modern understanding that our universe is much older, that many of the stars in other solar systems were formed long before our planet, and that our own sun was likewise formed before our planet, many Christian apologists have treated the Big Bang as evidence for God’s creation. In particular, apologists take the notion that our universe had a “beginning” as evidence for the cosmological argument that everything which has a beginning must have a cause (and this first cause must have been God).
To begin with, under a B-Theory of time (which will be discussed below), time is a dimension of space that, strictly speaking, has always existed. In that sense, the universe has no “beginning” in the sense that the universe emerged ex nihilo from a state of non-existence. Rather, if past time were finite, the dimension of space that is time would have an edge where t=0. This does not mean that there was a creation event before time, and, in fact, going to a point before t=0 would be like attempting to go “North” of the North Pole.
But furthermore, the rapid inflation of the universe, which may have occurred during the very first moments of the Big Bang, has led many physicists to believe that there were earlier stages of cosmic evolution before our universe was formed. One such theory is that our universe actually belongs to a much greater cosmos — a multiverse that consists of many (possibly infinitely many) universes. As Stanford physicist Andrei Linde explains (source here):
“For many years, cosmologists believed that the Universe from the very beginning looked like an expanding ball of fire. This explosive beginning of the Universe was called the big bang. In the end of the 70’s a different scenario of the evolution of the Universe was proposed. According to this scenario, the early universe came through the stage of inflation, exponentially rapid expansion in a kind of unstable vacuum-like state … Thus, inflation was a part of the big bang theory. Gradually, however, the big bang theory became a part of inflationary cosmology. Recent versions of inflationary theory assert that instead of being a single, expanding ball of fire described by the big bang theory, the universe looks like a huge growing fractal. It consists of many inflating balls that produce new balls, which in turn produce more new balls, ad infinitum. Therefore the evolution of the universe has no end and may have no beginning.”
The big picture of this inflation points towards a multiverse, i.e. a greater cosmos that is made up of multiple expanding universes rather than just one.
There are two major theories that point towards a multiverse cosmos. One is the Chaotic Inflation Theory. Advanced by Linde, the inflationary theory follows from current observations of the inflation in our universe to the conclusion that inflation has likewise formed other universes with different physical properties than our own. As Linde explains (source here):
“After inflation the universe becomes divided into different exponentially large domains inside which properties of elementary particles and even dimension of space-time may be different. Thus the universe looks like a multiverse consisting of many universes with different laws of low-energy physics operating in each of them. Thus, the new cosmological theory leads to a considerable modification of the standard point of view on the structure and evolution of the universe and on our own place in the world.”
Another multiverse theory, the Smolin Selection Theory, identifies a strong connection between black holes in our universe and the Big Bang. Black holes are formed when overwhelming gravity collapses matter down to a point of such high density that even light cannot escape. The Big Bang began in just such a state where matter and energy had been collapsed into an extremely dense and extremely hot point.
“Could there be any mechanism by which natural selection could work on the scale of the whole universe?
Once I asked the question, an answer appeared very quickly: the properties of the particles and the forces are selected to maximize the number of black holes the universe produces. This idea came right away, because of two ideas I was familiar with from my work on quantum gravity. The first is that inside a black hole, quantum effects remove the singularity that general relativity says is there — and that we know is there from the theorems of Penrose and Hawking — and a new region of the universe begins to expand as if from a big bang, there inside the black hole. I remember Bryce DeWitt, who is one of the great pioneers of quantum gravity, telling me about this idea shortly after I began to work for him, on my first postdoc. The second idea — which comes from John A. Wheeler, another great pioneer of the field — is that at such events the properties of the elementary particles and forces might change randomly. All I then needed to make a mechanism for natural selection was to assume that these changes are small, because reading Dawkins had taught me the importance for natural selection of incremental change by the accumulation of small changes in the gene. Then, with the universes as animals and the properties of the elementary particles as genes, I had a mechanism by which natural selection would act to produce universes with whatever choices of parameters would lead to the most production of black holes, since a black hole is the means by which a universe reproduces — that is, spawns another.”
Both of these theories follow from present scientific observations. In contrast, the God hypothesis does not follow from any definitive features within our universe that lead to an immaterial mind or a supernatural realm that lies beyond our own.
Is the multiverse theory testable? Although we may not be able to directly observe universes beyond our own, astronomer Luke Barnes in “Have cosmologists lost their minds in the multiverse?” explains:
“Unobservable entities aren’t necessarily out-of-bounds for science. For example, protons and neutrons are made of subatomic particles called quarks. While they cannot be observed directly, their existence and properties are inferred from the way particles behave when smashed together. But there is no such luxury with the multiverse. No signals from from other universes have or will ever bother our telescopes. While there is some debate about what actually makes a scientific theory, we should at least ask if the multiverse theory is testable? Does it make predictions that we can test in a laboratory or with our telescopes? The answer is yes, but perhaps not as you’d expect … If your multiverse theory generates its universes via some physical process, then that process may leave its fingerprints on this universe. This is what BICEP2 might have seen. Cosmologists think that in its earliest stages, the universe underwent an extraordinarily rapid expansion, known as inflation. In many versions of inflation, gravitational waves leave an imprint in fossil radiation, recently observed as characteristic swirls in this ancient light; a successful prediction of inflation. In some versions of inflation, the process that causes our universe to inflate is expected to produce huge numbers of other universes. Evidence for inflation isn’t exactly direct evidence for the multiverse, but it’s a start. We cannot see the creation of other universes, but if we have evidence for the physics that powers the universe generator then we have another piece of the puzzle.”
Likewise, a point that is also frequently missed is that, even if we could not scientifically test the multiverse theory, it is still a perfectly plausible philosophical position. That is, even if events prior to the Big Bang were untestable, we would have just as much philosophical warrant to believe that a multiverse lies behind the Big Bang expansion as we would for believing that a deity started the Big Bang. And, furthermore, the multiverse follows from present observations within our universe, so that, indeed, we have both more philosophical and scientific warrant for believing in a multiverse over a deity.
So, does our universe have any beginning at all? As physicist Andrei Linde explained above (source here):
“…the evolution of the universe has no end and may have no beginning.”
Apologists have other snares to trap people at this point. One is that, if the universe expands backwards into the past infinitely, then we could never reach the present moment, since time would have had to cross an infinite space to get to where we are now.
However, such an objection assumes and A-Theory of time. The A-Theory of time holds that only the present moment is real, and that the past is gone behind us and the future has not yet occurred. Most physicists, however, and even most professional philosophers , agree with the B-Theory of time. The B-Theory of time holds that all moments of time are equally real, and that time is simply a dimension of space, along with the dimensions of length, width, and height.
Under the B-Theory of time, asking how we could get to the present, if time is infinite, is akin to asking how we can get to point 0 on an infinite axis, if space is infinite. The answer is that one does not have to cross from -∞ to 0 to reach point 0, even an if infinite space lies between -∞ and 0. The reason why is that one does not cross any space at all. Point 0 simply exists on an axis that extends infinitely in each direction. In like manner, under a B-Theory of time, we did not cross any span of time (at least in a presentist sense) to reach the current moment. Rather, all time exists equally in both directions, and we are simply at a particular point in time.
For a further elaboration on the concept of time and infinity, I recommend professional philosopher Graham Oppy’s article “Time, Successive Addition, and Kalam Cosmological Arguments.”
Another possible problem for an infinite universe is that some multiverse theories suggest that, even if our universe was formed by chaotic inflation, there may have been a beginning to the chaotic inflation itself. In that sense, going to “before” the Big Bang only moves the problem back a peg further, as chaotic inflation may have a finite beginning that allegedly requires a cause (which an apologist may posit to be God).
A model of finite inflation has been proposed by physicist Alexander Vilenkin (and misrepresented by apologist William Craig, whose misrepresentation has been refuted extensively here), in which the inflation that caused our universe may have “began” at a certain point. These are Vilenkin’s own words on the matter (source here):
“We are then faced with the question of what happened before inflation. And whatever the answer is, we can keep asking: “And what happened before that?” So it seems that one of the most basic questions of cosmology – What was the beginning of the universe? – does not have a satisfactory answer. The only way around this problem of infinite regress that has been suggested so far is the idea that the universe would be spontaneously created out of nothing. We often hear that nothing can come out of nothing. Indeed, matter has positive energy, and energy conservation demands that any initial state should have the same energy. However, it is a mathematical fact that the energy in a closed universe is equal to zero. In such a universe, the positive energy of matter is exactly compensated by the negative energy of the gravitational field, so the total energy is zero. Another conserved quantity is the electric charge, but once again it turns out that the total charge must vanish in a closed universe. This is not difficult to understand. Suppose the universe has the form of a 3D sphere, and imagine placing a positive charge at the “south pole” of that sphere. The lines of force emanating from the charge will then converge at the north pole, indicating that there must be an equal negative charge there. Thus, you cannot add an electric charge anywhere in a closed system without adding and opposite charge someplace else. If all the conserved numbers of a closed universe are equal to zero, then there is nothing to prevent such a universe from being spontaneously created out of nothing.”
Remember also that it is meaningless to ask what happened “before” time. If there is a point where t=0, then you cannot go before this point anymore than you could go “North” of the North Pole.
The real question would be why there is a timeline after the zero, and not just t=0 (i.e. why the dimension of time is extended and not zeroed out). We might answer this by positing that there is a “cause” that exists at the same time as t=0, and thereby entails t–>nonzero. However, there is no reason to assume that such a cause must be a supernatural agent, which would be a far more complicated and speculative hypothesis (which I explain here) than simply positing a purely natural and mechanical cause.
Such a purely natural cause is being investigated by serious scientists. Here is an article from The Physics arXiv Blog (one of the top physics blogs on the web), summarizing an article from a team at the Wuhan Institute of Physics and Mathematics in China titled “Spontaneous Creation of the Universe from Nothing,” which explains:
“At the heart of their thinking is Heisenberg’s uncertainty principle. This allows a small empty space to come into existence probabilistically due to fluctuations in what physicists call the metastable false vacuum. When this happens, there are two possibilities. If this bubble of space does not expand rapidly, it disappears again almost instantly. But if the bubble can expand to a large enough size, then a universe is created in a way that is irreversible.”
Bear in mind that physicists such as Andrei Linde argue that cosmic inflation could extend infinitely into the past, and thus there would be universes all the way down. Modern cosmologists are not yet certain on whether we live in a past-finite or past-infinite universe, but, either way, there are non-theistic explanations of both, as discussed above. For more information about the multiverse theory and its relation to theism/atheism, check out physicist Victor Stenger’s upcoming book God and the Multiverse.
Another puzzling feature of our universe is the question of why we live in a universe that possesses minds (i.e. we ourselves) capable of observing/understanding the universe. In order for observation of the physical universe to be possible, the physical conditions within the universe must be conducive to producing life and conscious minds. The Anthropic Principle raises the question of whether our universe is impelled, in some sense, for conscious life to emerge, or whether there is a process of selection bias that allows our universe to have the correct life-supporting features. Apologists often focus on how, if our cosmological constants were slightly different, then our universe would be incapable of producing life. For example, atoms consist of protons, neutrons, and electrons. If protons were just 0.2% larger than they are in our universe, the would be unstable and would decay into simpler particles. Without them, atoms would not exist and neither would the building blocks for life. Likewise, if gravity were only slightly more powerful, stars would compress more tightly, be hotter, and denser. Rather than surviving billions of years, they would burn through their fuel faster and would not have a long enough duration to produce life. Apologists argue that these coincidences are too specific to have happened by chance, and thus an intelligent creator must have intervened to finely-tune our universe for life.
Apologists thus use the Anthropic Principle as evidence for the fine-tuning argument. First, bear in mind that many other complex or puzzling features of our universe have previously been thought to be too coincidental to happen without design. For example, the human eye was once thought to be too complex an arrangement to have happened without intelligent design. However, through the discovery of mutation and natural selection, biologists have now been able to completely demonstrate how the eye evolved due to (ironically) blind, mechanical forces (as shown here). As Nobel laureate Steven Weinberg explains (source here), “just as Darwin’s theory of evolution made it unnecessary to appeal to a benevolent designer to understand how life developed with such remarkable abilities to survive and breed,” the multiverse theory explains how the apparent design of the cosmological constants in our universe could evolve through purely natural processes.
The multiverse theory, in the form of both the Chaotic Inflation Theory and the Smolin Selection Theory, provides a theoretical framework in which there would be enough universes (and perhaps even a cosmic selection process) to allow for a particular universe with our life-supporting features. As physicist Victor Stenger in “Is the Universe Fine-Tuned for Us?” explains:
“If many universes beside our own exist, then the anthropic coincidences are a no-brainer. Within the framework of established knowledge of physics and cosmology, our universe could be one of many in a super-universe or multiverse. Linde … has proposed that a background space-time “foam” empty of matter and radiation will experience local quantum fluctuations in curvature, forming many bubbles of false vacuum that individually inflate into mini-universes with random characteristics. Each universe within the multiverse can have a different set of constants and physical laws. Some might have life of a form different from ours; others might have no life at all or something even more complex or so different that we cannot even imagine it. Obviously we are in one of those universes with life.”
For further elaboration for of how all of the cosmological constants and unique features of our universe can be explained as only illusory design, you can consult Dr. Stenger’s monograph on the subject, The Fallacy of Fine-Tuning: Why the Universe Is not Designed for Us.
Furthermore, the fine-tuning argument can be reversed against apologists. Even if our universe is able to produce life, the time and scale that is required is so massively inefficient that it makes it highly unlikely that these life-producing features were intelligently designed. In fact, our universe is overwhelming lethal and hostile to life, to such an extent that it appears to have been entirely undesigned. As naturalist philosopher Richard Carrier explains in “Finely Tuning a Killer Cosmos“:
“Even the [theist] proposal that God designed the universe, indeed “finely tuned” it to be the perfect mechanism for producing life, fails to predict the universe we see. A universe perfectly designed for life would easily, readily, and abundantly produce and sustain it. Most of the contents of that universe would be conducive to life or benefit life. Yet that is not what we see. Instead, almost the entire universe is lethal to life—in fact, if we put all the lethal vacuum of outer space swamped with deadly radiation into an area the size of a house, you would never find the comparably microscopic speck of area that sustains life. Would you conclude that the house was built to serve and benefit that subatomic speck? Hardly. Yet that is the house we live in. The [theistic] theory completely fails to predict this—while atheism predicts exactly this …When we look at how the universe is actually built, we do find that it appears perfectly designed after all—but not for producing life. Lee Smolin [“Did the Universe Evolve?“] has argued from the available scientific facts that our universe is probably the most perfect universe that could ever be arranged for producing black holes. He also explains how all the elements that would be required to finely tune a perfect black-hole-maker also make chemical life like ours an extremely rare but inevitable byproduct of such a universe. This means that if the universe was designed, it was not designed to make and sustain us, but to make and sustain black holes.”
Carrier further provides an analogy for how our universe could produce life without explicitly being designed to do so:
“Think about it. If you found a pair of scissors and didn’t know what they were designed for, you could hypothesize they were designed as a screwdriver, because scissors can, after all, drive screws. In fact, there is no way to design a pair of scissors that would prevent them being used as a screwdriver. But as soon as someone showed you that these scissors were far better designed to cut paper, and in fact are not the best design for driving screws, would you stubbornly hang on to your theory that they were designed to drive screws? No. You would realize it was obvious they were designed to cut paper, and their ability to drive screws is just an inevitable byproduct of their actual design. This is exactly what we are facing when we look at the universe: it is not very well designed for life, though life is an inevitable byproduct of what the universe was more obviously designed for: black holes. So if the universe was intelligently designed, it clearly was not designed for us.”
Naturalist Jeff Lowder likewise maintains a page titled “The Evidential Argument from Scale” with further resources and arguments for how the massive and inefficient size of our universe points towards atheistic naturalism.
So what kind of universe do we live in? All of the evidence points towards a metaphysical naturalist universe. As I discussed in my previous post, naturalism predicts a universe with no guiding teleology, goal-orientation, or design. Such is the universe that we inhabit. We live in a universe that is ludicrously large and poorly designed for sustaining life. Likewise, if scientific experts are correct about the multiverse theory, then there are countless more universes of dead space without the correct life-producing conditions. This greater cosmos of multiple universes, driven by inflation or selected for producing black holes, may have no beginning and no end. Even if there were a beginning of time where t=0, this would simply be the edge of a dimension of space, and could not be preceded anymore than there could be “North” of the North Pole. If there were a “cause” that caused t=0 to become t–>nonzero, there is no reason to believe that such a cause would be an immaterial supernatural mind, rather than a purely natural feature of our cosmos. Finally, the absurd scale and time of the universe, in comparison to the tiny accidental speck that produces life, suggests that there was no design at all, rather than a natural process of selection. Such natural selection has explained previous cases of illusory design before, as in the case of Darwin’s theory of evolution.
The naturalist cosmos and our place within it is perhaps best summed up in the words of Douglas Adams:
“Imagine a puddle waking up one morning and thinking, “This is an interesting world I find myself in — an interesting hole I find myself in — fits me rather neatly, doesn’t it? In fact it fits me staggeringly well, may have been made to have me in it!” This is such a powerful idea that as the sun rises in the sky and the air heats up and as, gradually, the puddle gets smaller and smaller, it’s still frantically hanging on to the notion that everything’s going to be alright, because this world was meant to have him in it, was built to have him in it; so the moment he disappears catches him rather by surprise. I think this may be something we need to be on the watch out for. We all know that at some point in the future the Universe will come to an end and at some other point, considerably in advance from that but still not immediately pressing, the sun will explode. We feel there’s plenty of time to worry about that, but on the other hand that’s a very dangerous thing to say.”
Part of metaphysical naturalism is breaking this puddle’s delusion, since, if there is any hope for us in the cosmos, it will certainly not come from the intervention of a deity (cf. A History of the End of the World). By recognizing the purely natural world we live in, however, we may be able to find the right technology that we need to manipulate nature for suiting our own purposes. That is the only way that we can live a finely-tuned existence, when we ourselves take design into our own hands. Neil deGrasse Tyson in the most recent episode of Cosmos: A Spacetime Odyssey titled “The Immortals” offers a vision of what this future world may look like.
We can only achieve this better future, however, when we properly understand the actual universe that we live in, rather than appeal to ancient texts that were written in an age of ignorance and superstition. That is why understanding the metaphysics of naturalism, including our cosmology, is crucial to having a map of reality that will guide us in the right direction.
 A PhilPapers survey of professional philosophers, who are either faculty or have a PhD, and who specialize in the Philosophy of Physical Science, finds that 44.4% agree with the B-Theory of time, 38.9% identify as “Other,” and only 16.7% agree with the A-Theory.