In this section of the book Carroll delves into how he believes the world works according to Core Theory and quantum mechanics. He uses these determinations as a springboard into discussing why the universe exists, and how God fits into this picture, or doesn't, as well as the discussion regarding whether there is a soul, and whether or not life will continue after death.
Abducting or deducting God?
Carroll begins to consider worldviews that would oppose his "poetic naturalism" -- one such worldview being that of theism. And what happens when we are confronted with two opposing ontologies that are situated on the same domain? Well, for Carroll it's the method of Bayesian reasoning and abductive logic all the way:
[F]or purposes of this discussion let's imagine that the prior credences for theism and atheism are about equal. Then all the heavy lifting will be done by the likelihoods -- how well the two ideas do in accounting for the world we actually see. (p. 146)So Carroll's plan is to look at the world and attempt to determine which ontology provides the best explanation for what we see, or don't see. We see evil in the world, then that scores points for atheism. We see consciousness in the world, chalk up a point for theism. Etc.
This might seem a good way to go about inferring which worldview is most reasonable to assume, but I maintain that's it's completely wrongheaded in this instance. First, as I mentioned in one of the previous reviews, abductive (Bayesian) reasoning is not the only kind of reasoning, and more importantly it's not the best kind of reasoning that should be utilized in this discussion. In everyday life and scientific reasoning, abduction is your best friend. If you're a scientist and you find that the liquid in a test tube has changed color, you use inference to the best explanation, plain and simple. But if you're attempting to determine whether the square root of two is a rational or an irrational number, abduction is the wrong tool to use -- you need deduction.
So, why then, should we use deduction when determining whether theism or atheism is true, and not pure abduction, as Carroll would have us do? Well, it comes down to who has the burden of proof: the theist. The theist is saying that there is in fact some positive reality that exists, and it is their burden to prove this. And how do they usually go about attempting to prove it? Through (mostly)logical deduction -- at least that's how the classical theists did it before Paley.  Thus, when weighing theism vs atheism, one needs to take the arguments that are being given by theists, which are deductive in nature, and determine whether they hold any merit. Appealing purely to abduction won't do any good, just like appealing to abduction to argue that the square root of two is rational will not be entertained by any mathematician. Contrary to Carroll, the heavy lifting is not done by likelihoods, but by deduction.
The point is that if theistic deductions are valid and sound then no amount of abductive inference will call this into question. And thus what needs to be determined is precisely the matter of if theistic deductions are indeed valid and sound or not -- which, again, is a job of deductive inference.
The more important point is that there are simply some beliefs that are so fundamental and metaphysical that a pragmatic method simply cannot comment on. Like it or not, abduction won't solve the realism/skepticism debate. It won't solve the free will/determinism debate. And it certainly will not solve the theism/atheism debate. Carroll wants to use a screwdriver for every job, when some jobs require a sledgehammer.
Whence the universe?
Carroll commits a whole chapter to exploring the question of why the universe exists, and why there is something rather than nothing. He begins by contemplating the answer of a necessary being in that of God but quickly casts it aside:
Poetic naturalists don't like to talk about necessities when it comes to the universe. They prefer to lay all the options out on the table, then try to figure out what our credences should be in each of them. (p. 196)First, it's irrelevant that poetic naturalists like Carroll "don't like" to talk about necessities when it comes to the universe. The relevant question is whether talk of necessity is appropriate when it comes to questions of fundamental metaphysics -- of which existential questions like "why is there something rather than nothing?" are a subset -- and surely it is. So, the fact that Carroll is allergic to necessity/contingency talk is not sufficient to cast that talk aside as if it were irrelevant -- and neither has Carroll given any warrant for doing so.
Second, and more importantly, the question being dealt with here is, again, of a significant metaphysical stature, and I don't see that abduction is the right tool to use here. When asking why there is something rather than nothing, what's really being asked is why existence should ontologically precede a complete lack of existence, and this is a deeply metaphysical question in nature, which most likely will have to yield to some type of existential necessity or brute fact -- if you believe in such nonsense. And the fact of the matter is that delving into the nature of existence is commonly a deductive, and not an abductive, endeavor. Thus, the poetic naturalist way of going about answering this detective story is already wrong-headed to begin with.
Nevertheless, let's see the blueprints that Carroll lays out to proceed in answering this question:
Let's start with the relatively straightforward, science-oriented question: could the universe exist all by itself, or does it need something to bring it into existence? [...] All we want to know is "Is the existence of the universe compatible with unbroken laws of nature, or do we need to look beyond those laws in order to account for it?" (p. 196-197)These are very relevant and important questions to our current inquiry. Carroll attempts to answer these questions by turning to science to settle the debate regarding whether or not the universe had a beginning -- his answer eventually terminating in a modest "we don't know."
The problem here, though, again stems from the fact that Carroll is ignorant to the fact that these are simply not the questions that science can answer in the first place -- "these" questions being the original questions he posed. For even if we could mathematically describe our universe as self-sustaining or existing by itself, this wouldn't actually make any progress in answering the existential question. For science only describes the behavior of that which already naturally exists, and it cannot tell you why the universe behaves in that way in the first place, or why it behaves this way as opposed to another way. To put it in a different vein, in order to have a behavior to describe you first need something which exists and does the behaving, and this means that existence is ontologically prior to behavior. Therefore, no description of behavior (which is all that science is) is sufficient to explain the existence of what does the behaving, and thus, science cannot in principle answer the question of why there is something rather than nothing. Sorry Carroll.
What this also entails, once again, is that Carroll is looking for an answer to the existential question utilizing the wrong tools. Since science cannot aid us in determining why something exists rather than nothing then it is irrelevant, to say the least, when it comes to this particular question -- sorry Lawrence Krauss.
However, Carroll is prepared (or so he thinks) to take on this line of thought:
For questions like this, however, the scientific answer doesn't always satisfy everyone. "Okay," they might say, "we understand that there can be a physical theory that describes a self-contained universe, without any external agent bringing it about or sustaining it. But that doesn't explain why it actually does exist. For that, we have to look outside science." (p. 201)Yes, this is exactly what I would say. Let's see how Carroll is going to set me straight:
Sometimes this angle of attack appeals to fundamental metaphysical principles, which are purportedly more foundational even than the laws of physics, and cannot be sensibly denied. In particular, the pre-Socratic Greek philosopher Parmenides put forward the famous maxim ex nihilo, nihil fit -- "out of nothing, nothing comes." [...] According to this line of thought, it doesn't matter if physicists can cook up self-contained theories in which the cosmos has a first moment of time; those theories must necessarily be incomplete since they violate this cherished principle.
This is perhaps the most egregious example of begging the question in the history of the universe. We are asking whether the universe could come into existence without anything causing it. The response is "No, because nothing comes into existence without being caused." How do we know that? It can't be because we have never seen it happen; the universe is different from the various things inside the universe that we have actually experienced in our lives. And it can't be because we can't imagine it happening or because it's impossible to construct sensible models in which it happens, since both the imagining and the construction of models have manifestly happened. (p. 201-202)Alright, there's a lot to unpack here. First, notice that Carroll has actually side-stepped the original point that he was claiming to address -- namely, that talk of scientific models doesn't actually address the question of why something exists in the first place. (Note that he does later on say that we may never know why the universe exists, and that its existence might simply be a brute fact. You know what my response is.)
Second, to appeal to fundamental metaphysical principles to call scientific models into question, or to highlight their incompleteness, is not to beg the question. For these principles are seen, by those promulgating them, as necessary conditions of reality; that is, they're seen as conditions that hold in any possible world and are the things that even make science possible in the first place. Thus, to claim that a scientific model cannot overthrow them is not to beg the question. It would beg the question if the individual promulgating said principles had no justification for their necessity. But this would have to be demonstrated by the likes of Carroll, which, to give him credit, he does attempt to do, which brings me to my next, and third, point.
Carroll asks a good question: how does one know that metaphysical principles like the law of causality are immutable? The answer is that we know this because those very propositions are formed through relations of concepts that we abstract from reality, which, as we saw in the last post, we must have objective knowledge of -- on pain of contradiction. Another way to put it is that our knowledge is dictated by reality, and not the other way around, and thus the reason why we know that principles like the law of causality are immutable is because these principles are themselves grounded in the objective nature of reality. 
Fourth, it is actually Carroll who begs the question here, though he does it so well that it's hard to catch. To revisit my first point above, he claims that to address the fact that scientific models don't answer the "Why?" of existence, individuals sometimes resort to metaphysical principles. But how does he argue against these principles? By appealing to the very physical models of the universe he already utilized and was questioned on! That is to say, based off of Carroll's argumentation, we could construct the following conversation:
Carroll: We can easily construct physical models of the universe which are self-sustaining.
Me: But those models are purely descriptive and incomplete, and don't answer why something exists in the first place.
Carroll: Where are we to look for this "Why?"
Me: To metaphysical principles like "that which is moved from potency to act is moved by that which is already actual."
Carroll: But this principle is false, since we have already constructed physical models which are self-sustaining.
Round and round we go. Hopefully the attentive reader notices that Carroll would simply keep begging the question regarding his self-sustaining physical models.
Furthermore, the more crucial point is that since science is only quantitatively based, it does not, in its equations, capture notions of causality -- something Carroll has articulated multiple times in the book. Therefore, even though we might be able to construct a model of reality that is self-sustaining, and self-contained, as far as physics is concerned, this does not actually equate to forming a model of the universe that is not contingent upon, and not caused by, anything else. Thus, Carroll's self-sustained models are actually completely irrelevant to the current discussion.
Carroll then briefly returns to the notion of God as an answer to the existential question:
Theists think they have a better answer: God exists, and the reason why the universe exists in this particular way is because that's how God wanted it to be. Naturalists tend to find this unpersuasive: Why does God exist? But there's an answer to that, or at least an attempted one, which we already alluded to at the beginning of this chapter. The universe, according to this line of reasoning, is contingent; it didn't have to exist, and it could have been otherwise, so its existence demands an explanation. But God is a necessary being; there is no optionality about his existence, so no further explanation is required.
Except that God isn't a necessary being, because there are no such things as necessary beings. All sorts of versions of reality are possible, some of which have entities one would reasonably identify with God, and some of which don't. We can't short-circuit the difficult task of figuring out what kind of universe we live in by relying on a priori principles. (p. 203)Again, there's a lot to unpack here. First, I want to focus on Carroll's comments on God as a necessary being, for he's only begging the question here. He literally gives absolutely no justification or substantiation for the claim that no necessary beings exist. He hasn't even come close to attempting to do the philosophical leg-work that would warrant him in making such an audacious claim.
Second, the only semblance of an argument Carroll does give in favor of God not being a necessary being is that of the fact that we can conceive of other possible worlds where there no such God. But again, Carroll hasn't done the leg-work to demonstrate this. For if we arrive at a logical deduction of what God is, as classical theists claim we can, then by "God" we literally mean "that whose essence is to exist," which means that by definition God cannot not exist. But this entails that there actually is no world of which we can conceive where God does not exist , and thus Carroll is wrong.
Third, Carroll actually refutes himself here when dismissing talk of a priori principles. Remember that Carroll is big on empiricism, and believes that the only way we can have genuine knowledge is to actually look at reality -- thus, a priori philosophy is moot in his eyes. However, Carroll's point in his latter paragraph is predicated on "all sorts of versions of reality" being ontologically possible -- that is, he's employing the notion of modal logic, an a priori endeavor. How does Carroll know that reality enjoys various ontological "possibilities"? He might say, "because of the fact we can imagine them" -- he seems to say as much on page 203. But that immediately commits one to the idea that possibility is grounded in the imagination; yet how would Carroll ground that idea? That is, why does Carroll believe that our imagination is capable of telling us anything true about the nature of reality? The point here that I'm trying to make is that any answers to these questions will necessarily be founded on a priori principles, the very thing Carroll is allergic to and vehemently opposes, as we saw last review. But, were he to give his beliefs a little more thought, he'd see that he ends up falling on his own sword, as it were.
In any event, Carroll conjures up no answer to the existential question of why the universe exists in the first place; though he should not be faulted for this. What he is to be faulted for is his sloppy logic utilized to throw opposing answers, like that of theism, under the bus. And thus it doesn't seem like his poetic naturalism is properly justified.
 Don't get me wrong. I know that many theists have attempted to persuade individuals that God exists by telling them to look at the stars, or the beauty that we perceive in the world etc., and this no doubt is done in the vein of abduction. But this is usually not done to satisfy one's burden of proof, at least in the sense of what we mean by "proof".
Carroll also visits this idea earlier in his book on page 116 wherein he claims that "[beliefs] aren't (try as we may) founded on unimpeachable principles that can't be questioned." But this is false. If you push back on the justifications for propositions of knowledge further and further, you will arrive at a foundation of first principles that are axiomatic and, contrary to Carroll, cannot be questioned.
 Note that to imagine is not to conceive, in that I can conceive of something without imagining it and vice versa. Carroll constantly conflates the two throughout his book.