MODERATOR: Let’s give them both another hand. [applause] This was just amazing. The one thing I am amazed by is that there are great disagreements about time but both of them stayed on time. [laughter] Thanks, guys! Come on up to the podium. Let me explain how this is going to work. I need to get my notes here. My wife gets very nervous when it's just my stream of consciousness working. [laughter]
We have a microphone in each aisle for questions. The aisle over here on Sean's side is for questions for Sean Carroll. The aisle over here by Bill's side is for questions for Bill Craig. And we're going to alternate from one to the other, and we'll have an even number of questions—alright? When a question is asked to Sean, Sean will have two minutes to answer. If Bill wants to respond he'll have up to one minute. And vice versa—when a question is asked to Bill he has up to two minutes to answer, and Sean has up to one minute.
Let me give some instructions to those who are asking questions. Number one: state your question in a hurry, like twenty seconds, okay? Number two: make sure that it's a real question. [laughter]
The way to make sure that you're asking real questions is ask yourself a question. Ask yourself this question: was I paid to come here? [laughter] Exactly! If you were not paid to come here then you are welcome to ask a question but you are not invited to lecture. So make sure it's a real question. Second, ask yourself this question: will everyone benefit from hearing this question? Is it a question that's going to shed light, to get at more truth? Or is it more akin to some interesting thoughts you had one night after your third highball? You've heard it said, there is no such thing as a stupid question. That's not true. [laughter] That's a stupid saying. And my last instruction would be: you only get one question. When you ask your question, step away from the microphone. No follow-ups, unless Sean or Bill asks you. If they don't understand what you're saying and they ask you a question, you can clarify it. So we can get more questions in and everyone will be happier. So come to the microphones now, and we will begin.
One other thing: here at the Greer-Heard forum we follow Robert's Rules. My name is Robert, I make the rules. [laughter]
Question 1: Hey, Dr. Carroll, how are you doing? Thank you for being here tonight, sir. In your polemic tonight on theism you said something like, “Look, if you have a fully explainable model, why do you keep looking for something else to add?” Okay? Now, my question is something like this: if you took as a metaphor for the universe, say, that we have a complete and entire physical explanation for the existence of the jet engine – you know, we can talk about internal combustion, all the things that go into making it and so forth – but does that complete knowledge mean that Frank Whittle didn't exist? Does a fully accurate mathematical model make this so? My question is this, exactly: isn't this a category mistake to assume that it does; namely, that law and mechanism does away with personal agency?
Dr. Carroll: Great. This is being recorded, I don't need to repeat the question—right? So his question got on to the tape? Okay. Yeah, so, it's a very good question and I think the answer is the universe is different than things inside the universe. As I tried to explain, there is a reason why there are reasons why. There are reasons why in our everyday life it is perfectly correct to speak a language of causation and explanation and invention and creation, and when you look carefully what those reasons are, they don't apply to the universe. The universe isn't part of a bigger structure in which there are patterns, evolution laws, arrows of time, expectations for what should happen. So a jet engine and a universe are just not very analogous to each other.
Dr. Craig: It seems to me that that's just fantastic, to think that the universe could just come into being from non-being; that it just pops into existence. And, as I said, if one says that that is possible, then you're confronted with the difficulty: why only universes? It seems to me then that everything and anything would come into being from nothing because there's nothing about nothing that could make it discriminate between universes and anything else. So it seems to me that this is a difference without a difference. I would say that the condition that applies to the universe that makes the causal principle relevant would be its beginning to exist. If a horse begins to exist, there's got to be a cause for that. If a building begins to exist, there's got to be a cause for that. Similarly if the universe begins to exist, there needs to be a cause for that. And in that respect the conditions for the causal principle do apply. Sorry, I'm out of time!
Question 2: Dr. Craig, what would you say to a Thomist, a follower of Thomas Aquinas, who says, “I have good arguments for God such as Aquinas' Five Ways that are based on indubitable metaphysical principles. It would be imprudent to advance a theistic argument that rests even partly on modern science since science can change and if some theistic argument loses face as science changes so does theism.?” Dr. Craig, what about this charge of imprudence from the Thomist.
Dr. Craig: Yes, I would say that Thomas Aquinas' own metaphysical principles are highly dubious and in doubt, and that therefore I have little confidence that his arguments are, as he claimed, demonstrations. Aquinas was familiar with the kalam cosmological argument. This is a very ancient argument, and he was aware of the Muslim medieval thinkers who championed it. And Aquinas said if the universe did began to exist, then clearly there had to be a cause of the beginning and of motion. But he thought you couldn’t prove with demonstrative certainty that the universe did begin to exist. (Of course, they had none of the modern empirical evidence.) But I am persuaded, and I think Aquinas would agree, that the philosophical arguments for the beginning were good probability arguments, even if they weren't mathematical demonstrations. So I think Aquinas simply raised the bar too high for what constitutes a good argument for God's existence. We don't need to have certainty or mathematical demonstrability. All we need to do is offer arguments that are logically valid, have true premises, and the premises are more plausibly true than not. And if that's right, then that's a good argument for the conclusion. And I think we've got such arguments today, and we shouldn't be preoccupied with Aquinas' concern for metaphysical or mathematical demonstration.
Dr. Carroll: One of the architects of the Big Bang model was George Lemaître, who's a Belgian physicist, mathematical physicist, MIT and Harvard graduate, and also a Jesuit priest. And later in life, in the 1950s, he was serving on a papal commission because the Pope at the time wanted to put forward a statement that said, “Look! The Big Bang! Excellent evidence for the existence of God.” And Lemaître stopped him from doing that. He said, “No, you can't get your peanut butter of theology mixed up with the chocolate of science. It does not actually taste great together because, who knows, someday some smartass will come up with a theory of the universe that is eternal and there isn't a Big Bang anymore.” Dr. Craig and I are on the same side. We think that Lemaître was wrong to make that kind of statement. We both believe that if you're going to be an intellectually honest theist you need to accord with the best data from the universe. And as we both agree, science isn't in the job of proving things with metaphysical certitude. It says that models get better and better at fitting the data. I think that works just as well for theism as it does for naturalism.
Question 3: Dr. Carroll, thanks for being here tonight. My question: at the end of your first speech you mentioned how, in a nutshell, the theist weasels his way out of predictions that we would make based on the evidence. My question is, though: coming at it, that seems to be assuming that naturalism is some sort of default position and that theism is just adding one step on. My question would be that: do you not find that naturalism is a sort of a bent, an angle, that you're coming at in that you allow nothing in that realm? Because, I mean granted I know that's what naturalism is, but that you're so shut off from the beginning that nothing could ever, ever, ever meet the evidence. Like Lawrence Krauss says, even if it was written in the sky, he would maybe consider it.
Dr. Carroll: That's right, yeah, I think this is a good point. Personally I think that there would be no problem for me to be persuaded out of naturalism. Alright, the roof is not falling on me. [laughter]. But I think it's a matter of what is the model that best fits the data. Again, five hundred years ago I would have been a committed theist because that was the best we could have done at the time. So I think that it is not an assumption. Some people try to sometimes say that science or naturalists start from an assumption of naturalism so they just simply won't consider alternatives. I'm very happy to consider alternatives. I think that if there were some phenomena in the world which really looked exactly like some religious tradition was saying should happen and was miraculous, was seemingly violating the laws of physics, what would scientists do in that situation? They would not say, “Oh, we're not allowed to think about this because we agreed yesterday at faculty tea that the world was a natural world.” I think they would try to come up with the best explanation. If the best explanation is not naturalism, then I would buy that. I will say that naturalism seems to me to be a priori simpler than theism because naturalism is the natural world, theism has the natural world and something else that I think is ill-defined. But I didn't actually use that. I think in a proper quantitative Bayesian probability analysis my prior for naturalism is higher than my prior for theism, but overwhelming evidence will always take care of that. I just don't think it's there.
Dr. Craig: Both the naturalist and the theist can be stubbornly committed to their worldviews and not allow contrary evidence to overthrow it. Naturalists are just as adept as theists at explaining away evidence that they find inconvenient—I mean, even to the extent of asserting that the universe popped into being out of nothing! So that's a charge that, I think, goes both ways. It would be possible to falsify theism, for example, by showing a contradiction in the concept of God, as some have sought to do – that there could not be, for example, an omniscient person or a timeless person or something of that sort. So that would be a means of falsifying theism if one could go that route.
Question 4: Dr. Craig, I'd like to understand whether the kalam argument (because I am struggling with this) . . . You're stating that the universe has a beginning, and then you evoke cause and effect, but cause and effect is a temporal concept. So if there is no time?
Dr. Craig: Is a what?
Question 4: It is a temporal concept; it makes sense if time exists. But before the universe there's no time, and considering that, why would you need a cause when the concept of cause and effect does not make really any sense?
Dr. Craig: Now, when you say that cause and effect are temporal concepts, what do you mean by that?
Question 4: Well, that you have a cause has always precedes the effect.
Dr. Craig: Ah, that's what I thought you might think! Yeah, I don't think that's at all true. Don't you think that causes and effects can be simultaneous?
Question 4: If they are then God and universe came into being at the same time, then why would you need God to explain the birth of the universe because they're born at the same time?
Dr. Craig: Okay, so you are willing to grant that causes and their effects can be simultaneous—right?
Question 4: Sure.
Dr. Craig: Okay, yes, I think that that's evident. So, what I would say is that God's creation of the universe is simultaneous with the universe’s coming into being. And what could be more obvious than that, when you think about it? When else could it come into being than at the moment when God created it? So my own studied view of God's relationship to time – which is a terribly interesting subject – is that God is timeless without creation and he is in time from the moment of creation on. The exercise of causal power by which God brings the universe into being marks God's entrance, as it were, into time in virtue of his causal relationship with the effect that he brings about. So I don't think causes do need to precede their effects temporally; they can be simultaneous with them. And in the case of creation I would say the universe comes into being at t=0, and that is the same moment at which God causes the universe to come into being.
Dr. Carroll: I'm pretty sure nobody cares about my opinion of God's atemporality, [laughter] so I will use this as an excuse to reiterate my objection to the language of coming into existence or popping into existence. That is not what the universe does even in models where the universe has a beginning, a first moment. Because the verb popping, the verb to pop, has a temporal connotation, is the word I'm looking for. It sounds as if you waited a while, and then, pop, there was the universe. But that's exactly wrong. The correct statement is that there are models that are complete and consistent in which there is a first moment of time. That is not the same as to say there was some process by which the universe popped into being. That's yet another difference between the universe and things inside the universe.
Question 5: Dr. Carroll, you said in prior talks that in the laws of physics that we observe today there's no room for free will. I'd like to know – granted that I consider you to be a rational, critical thinker – how do you reconcile critical thinking if at the same time you believe we don't have the free will to choose between true and false premises and valid and invalid logic. If those choices are made for you how is anything anybody says not immediately irrational?
Dr. Carroll: I know I'm in trouble when someone says “I consider you to be a rational thinker” before they ask me the question. [laughter] I'm not exactly sure what you read. I think if you read carefully, I believe in free will. I'm pro-free will. I think of free will as an emergent concept in a universe which at the fundamental level is completely mechanistic. I think there are laws of physics that do not involve what we call a libertarian approach to free will. I do not think that human beings supersede the laws of physics. I think that human beings are collections of elementary particles interacting according to the laws of physics. And if I were to, say, write down every single particle in my body and I had a Leplace's demon level of computation ability, I could predict what I would do. But I don't have any of that. I don't have the information, the micro-state of my quantum mechanical wave function, and therefore the vocabulary I use to describe myself is as human being making choices according to rational principles. And I think that it is absolutely legitimate in that framework to say free will is real. The most I ever wrote on free will was a short blog post called “Free will is as Real as Baseball.” Baseball is nowhere to be found in the fundamental laws of physics. It is a description at a collective level of things that happen in the macroscopic world. That doesn't mean that baseball doesn't exist, it just means that it's not there in the fundamental laws. I think that free will is exactly the same way. I think there is nothing wrong with using the language of people making choices, people being correct or incorrect.
Dr. Craig: Well, it seems to me that on your view, free will is ultimately illusory because everything we do is determined by what goes on on the fundamental level. And therefore, even though I have the illusion of free will, if I could really understand it, I would see that, in fact, I am determined to do everything that I do—including believing in determinism, which makes my choice to believe in determinism, it seems to me, irrational—or arational, I should say. I'm simply determined to believe in determinism. So I don't think it's helpful to talk about free will as an emergent reality when at a fundamental level you're affirming determinism. Then it's freedom only in name and not in reality, and in that case I think the questioner is right—it's very difficult to see how anything I do is rational. It's just like a tree growing a branch. It's all determined by mindless forces.
Question 6: Dr. Craig, it's an honor to speak with you tonight. I was going to ask Dr. Carroll something, but the line was so long, and I like short lines. So I came over here. [laughter] I'm not an atheist.
Dr. Craig: You could say, “If you were Dr. Carroll, what would you . . .” [laughter]
Question 6: There you go! I'm not an atheist, an agnostic, or a classical theist. I feel like there's a middle camp between the two of you that's ignored, and I'm more along the lines of a panentheist and along the lines of Spinoza and Einstein, and I think that that whole discussion gets lost here tonight. But the real question I want to get to and the important one, I think, is what Roger Penrose talks about with the necessity of conscious observation and the neglect of the Copenhagen interpretation of quantum mechanics among practicing physicists who seem to ignore the necessity of conscious observation creating quantum decoherence. And I wanted to find out what you thought about Roger Penrose and his ideas. Thank you.
Dr. Craig: Well, there are at least ten different physical interpretations of the equations of quantum mechanics, and they're all empirically equivalent, they're mathematically consistent, and no one knows which, if any, of them is the correct physical interpretation. I'm inclined to agree with philosophers of science who think of the traditional Copenhagen Interpretation as really just quite unintelligible. And I'm therefore more inclined to some sort of deterministic theory of quantum mechanics, like David Bohm's quantum mechanics. [laughter] Now I know that Sean Carroll holds to Everett's Many Worlds Interpretation; but that, again, seems to me to be just fantastic and has difficulty making sense out of the probabilities in quantum theory. But basically I don't think we need to decide. No one knows for sure what is the correct physical interpretation. It works, and that's what the practicing scientist is concerned with. But it remains a matter of deep debate as to how to understand it.
Dr. Carroll: Well, I'm glad we found another very important area of agreement between Dr. Craig and myself. The Copenhagen interpretation is basically nonsense. No thoughtful person still holds to it, and yet we teach it to all of our undergraduates—that's kind of a scandal. [laughter] And no one knows what the right answer is; I would also agree with that. I do hold to the Many Worlds interpretation. I think that you see it's kind of a consistent split that we have because people, when faced with the statement of the Many Worlds interpretation, it bothers them at an emotional level. I mean, where do you put all of those worlds? How do you fit them into the universe? But when you look at the level of the equations, it is the simplest possible interpretation of quantum mechanics. There are important questions that are still raised about it. I'm also writing papers about that. I think these are important issues to be addressed. But I judge simplicity by the number of ideas and concepts, not by the number of universes.
Question 7: Well, thank you for taking my question. Assume we had a model of the universe that corresponds to reality concerning all material things. Is it still logically possible to affirm the existence of a God?
Dr. Carroll: Yes. [laughter]
Dr. Craig: I didn't hear the final words – is it still possible, what?
Dr. Carroll: Yeah, maybe say the whole thing over again.
Question 7: Yeah, one more time; I'm sorry. Assume we had a model of the universe that corresponds to reality concerning all material things. Is it still logically possible to affirm the existence of a God.
Dr. Carroll: Good. So, yes.
Dr. Craig: Sure.
Dr. Carroll: You can. It's logically possible to assert a whole bunch of things. I mean, it's logically possible to assert that Isaac Newton had the right theory of gravity and Einstein didn't. It's logically possible to assert the steady state theory. You can probably find . . . I get emails from people who believe this. They're not very logical people, admittedly. But the way that science goes about deciding on theories is not on the basis of logic alone. You want your theories to be logical—I think that's the minimum requirement. But there are many, many logical theories. One of them is that we're all living in a computer simulation, there's a mad scientist out there. One of them is that none of you exist and I'm a brain in a vat. These are all logical possibilities. And about a similar level of plausibility in my mind is there's the logical possibility that we live in a world that always obeys the laws of physics and yet God created it and is hiding from us. So it is absolutely logically possible—I don't give it a lot of credence.
Dr. Craig: Yeah, logical possibility is simply too easy. And therefore, I think, you probably meant something, perhaps, different than just mere logical possibility. What we're talking about is, maybe, metaphysical possibility, or plausibility? Those are the real issues that, I think, are important because it would be pretty surprising if you could show that something like this would be logically impossible.
Question 8: Dr. Craig, you've been very skeptical about the idea of universes just popping into existence. Does cosmology have anything to say about where God might have come from? Or are we allowed to think that he could have popped into existence?
Dr. Craig: No, obviously cosmology would not have anything to say about where God came from because God is a non-physical, transcendent entity beyond the universe. That's why I used the word transcendent in that argument – this is something beyond the universe. The universe is defined as all contiguous physical reality. But I do want to take this opportunity to highlight for you a very significant difference between Sean and myself that is a philosophical difference that has tremendous impact upon this whole debate. And that has to do with this idea of “popping into existence.” If I'm not mistaken, Dr. Carroll holds to what is called a tenseless theory of time. That is to say, past, present, and future events are all equally real. Temporal becoming is merely a subjective illusion of human consciousness. There is nothing privileged about the present, ontologically speaking. I hold to quite a different view of time. I think that temporal becoming is a real and objective feature of the universe. The future doesn't in any sense exist; things really do come into being and go out of being. And that's why I use the language of popping into existence. Not because I illicitly presuppose time prior to the origin of the universe, but because I believe in a tensed theory of time which affirms the objectivity of temporal becoming. And on that view the beginning of the universe does not just tenselessly exist. The universe comes into being, and surely that requires a cause. Now this is not just an unfounded metaphysical assumption on my part. I've written two books on this in which I defend the tensed theory of time, giving arguments for it and answering objections against it, and then I attack the tenseless theory of time, giving arguments against it and answering arguments for it.[32] But this is a huge metaphysical assumption that underlies this debate and divides us.
Dr. Carroll: So I will confess, I don't know. This is not answering your question but it's a confession that as a scientist there is this enormous temptation that I am constantly resisting when I am in dialogue between science and theology which is that as theologians talk about the relationship between God and time, or God's status as necessary or anything like that, there's a big part of me that wants to say, “Why are you working so hard to extract yourself from these dilemmas when you can just say God doesn't exist?” It just sounds crazy. And then I realize I'm a cosmologist. And the same people could say the same thing about everything that I say. There's plenty of things that I say that sound crazy. So all I'm saying is that these are difficult, interesting questions, and it's very, very hard on the basis of thinking alone to get the right answers. That's why scientists have this huge advantage – we collect data.
Question 9: Dr. Carroll, you asserted that theism is unreasonable at least in part because the term God is poorly defined. So at the end of your first talk you said, “The solution to the problem that, from a theist's point of view, the world is not as we would predict, is easily solvable because of the flexibility of the terminology of God. So the theist can simply form any of hundreds of models of God that explain why the world is the way it is while maintaining the creative agency of God. And that's unreasonable.” But when you want to show the plausibility of an eternal universe you build a model and you showed seventeen of those and you said that all of them could work, but you don't think that any of them are right. They could be right but you don't think they're right. And that is reasonable. And I'm just wondering if you could clear up for me how that's consistent.
Dr. Carroll: Sure, that's fine. I think there is a difference in principle between the theist trying to use the idea of God to explain all these different aspects of the universe and the scientist developing many, many mutually inconsistent models and not know which one is right until they're developed. I think that with every one of these scientific models there is an expectation, indeed a demand, that when we understand the model perfectly it will make absolutely unambiguous “unwiggle-out-able-of” predictions about what the universe is like. I think this is not in principle possible in theism. I think – and different theists probably have different expectations about this – but I think that theists would not claim that once we understand God perfectly we can predict the mass of the Higgs Boson. But a physicist would claim that once we have the correct theory of everything we will be able to predict the mass of the Higgs Boson, and I think that's an absolutely crucial distinction.
Dr. Craig: I love this question because in the same way that the scientist develops models of the universe in order to understand it, the theologian does the same thing with respect to God – different models of God, understanding what he's like. And for Christians, the biblical data concerning God is underdeterminative. There's a great deal of latitude in developing your model or concept of God. For example, one of the classic questions is, “Is God timeless or is he infinite throughout all time?” And theologians develop different models of God and time, and then these models are tested. They're not tested by predictability; but they're tested by their coherence and by how well, for example, they would explain how an eternal being could create the universe, or how he could know, for example, tensed facts. I've written a great deal on this, and so you're quite right in saying it's analogous or parallel.
Question 10: Yeah, Dr Craig, you use the Borde-Guth-Vilenkin theory to justify an absolute beginning of the universe, and I was curious how you would address the point that was brought up about Guth probably holding that the universe in fact was eternal.
Dr. Craig: I haven’t spoken to him about it. I have spoken with Vilenkin. I think that they would agree that the theorem under this single stated condition shows that classical space-time did have to have a beginning, and Guth doesn't dispute that. He says that. Now when he holds up a little sign saying “I think the universe is probably eternal,” that's probably just reflecting a sort of personal preference or skepticism that maybe we'll find a quantum theory or something that will be a non-classical model that will restore the eternality of the universe. That could be his predisposition or his hope or hunch or something of that sort. But in terms of scientific evidence, there's no evidence at all that the universe is beginningless. As Vilenkin said, all of the evidence is on one side of the scale, that the universe began to exist, and there are no models of a beginningless universe that are successful. So I don't know exactly what he meant by that. But I think we do know that the implications of the theorem are that any model that falls under its single condition will have a beginning to classical space-time. And also I would say that models that don't fall under that condition usually always have other problems, as well. And then I argued that this quantum gravity regime, if there was such a thing that preceded the classical space-time regime, that marked the beginning of the universe, if the universe didn't begin at the classical space-time boundary.
Dr. Carroll: So I don't think it's the right thing to say that the Borde-Guth-Vilenkin theorem says that the classical universe had a beginning. The part of the universe that we can describe using classical space-time had a beginning just like this room had a beginning. But that says nothing at all about the universe as a whole. Alan Guth does not believe the universe is eternal because it's a hunch or personal preference. It's because he's a scientist and he's trying to develop models that fit the data. We have puzzles in cosmology. Given his knowledge of the models, he believes the best way forward, the most promising way forward, are the models in which the universe is eternal. He knows that there is a theorem saying if you obey the rules of quantum mechanics under the assumptions I gave the universe must be eternal. He knows the early universe had a low entropy and the best possible explanation we currently have for dynamically explaining that involves an eternal cosmology. This is exactly how scientists work all the time.
Question 11: Dr. Carroll, someone actually got to this question earlier, so just kind of a repeat and maybe you have some further comment on it. But suppose there was, you know, a naturalistic model for the universe and everything. What would your rebuttal be for someone who said there is yet a God that still works outside that model? Those might kind of be unfalsifiable but I'd still like a comment on that.
Dr. Carroll: Sure, I think that, again, it is absolutely conceivable. Let's go all the way to the extreme. I completely can conceive of a universe that was brought into existence by God who was omnipotent and so forth and for whatever reason God has chosen to be completely invisible and the universe runs by purely naturalistic principles. In that case I'm not saying that it is logically possible or even that it is illegitimate to conceive of that possibility. I just say it gets you nothing. By all of the conventional standards of scientific or even philosophical explanation, if I have two possible models that fit what we observe about the universe and one of them has less stuff, less ideas, it is more self-contained, is more rigid and well-defined than the other one, I'm going to prefer that one. I'm never going to say I completely rule the other one out. And this is not a completely hypothetical circumstance. Cosmology, quantum mechanics, quantum field theory, particle physics are full of many, many models that are in principle compatible with the data, but only if you take some parameters and push them out to where they shouldn't be, make them very, very small, make them very, very invisible. We put limits on our theories. We do not rule them out entirely. But when the limits, the constraints, becomes so strong the theories become uninteresting. We have a better way of moving forward. To me that's the situation with naturalism vs. theism.
Dr. Craig: The arguments that I've offered tonight are consistent with the universe’s being self-contained in the way that Dr. Carroll described. So that needn't be an issue of debate between us. But I don't see any reason to think that the universe is self-contained. I don't see any reason at all to think that the transcendent God doesn't act miraculously in the world. And there's simply no way that Dr. Carroll, as a scientist, could know that God never acts miraculously in the universe. So that the idea that the universe is causally closed or self-contained is really a naturalistic article of faith. It's a metaphysical presupposition, not an inference drawn on the basis of science.
Question 12: Dr. Craig, I really have enjoyed listening to both of you today. My question is . . .
Dr. Craig: Can you speak directly into the mic, please?
Question 12: Can you hear me now? [laughter]
Dr. Craig: Yes!
Question 12: Oftentimes when particularly believers or theists are talking about religion inside the arena of religion they are very, very comfortable, they know what they're talking about, but when they leave that arena and they go into places and talk about cosmology or they talk about medicine, it seems like that they are trying to make their religious beliefs fit into that sphere. So my question is this, and given that you said a few seconds ago God is not of this world or bigger than this world, why would he find it important to have a discussion about medicine, or find it important to have a discussion about the stars? Why would that be significant or relevant to him? Because, I mean, he is omnipotent.
Dr. Craig: As a systematic theologian, I am committed to having what I call a synoptic worldview, that is to say, a worldview that takes into account all of the data of human experience, not only what we learn from revealed truth in theology, but also from science, from history, from psychology, and the humanities. As a Christian I want to have a world and life view that makes sense of reality. And so I think that's why the Christian is vitally interested in these subjects and why I as a philosopher and theologian am terribly interested in these scientific theories about the origin of the universe, about the fundamental nature of physical reality, about the origin and evolution of biological complexity. I want to have a worldview that makes sense of the data of science. And I think that's one of the great things about the Christian worldview, that it does form a coherent worldview that answers our deepest questions and yet is consistent with what we learn from other sources of knowledge. So that's why I am committed to the project of developing this sort of synoptic world and life view.
Dr. Carroll: I hesitate when it comes to my job to tell believers what to think. And then I do it. So I'm not a believer but if I were a believer, if I were a theist, to me I would think that the fact of my theism would be absolutely central to everything I believed about the world in all of its aspects. I think that there's a modern tendency to try to shield religious belief and practice from the encroachment of scientific knowledge by saying, well, my religion has to do with my practice and my values but nothing to do with the physical world, the biological world, the scientific world. I think that that is actually a much less intellectually honest point of view than one like Dr. Craig's that engages with the full picture.
Question 13: Dr. Carroll, I'm going to try to phrase this without using terms I know you don't like—make this a how question instead of a why question. If our universe, our observable universe, had a first moment in time, and naturalism is true then it would seem that we need to explain that with some sort of eternal existing set of conditions, and they would have to be necessary and sufficient to produce the effect, which is our universe coming into being or having a first moment in time. So the difficulty seems to be that if we have an eternally existing set of causal conditions that are sufficient to produce the effect, why isn't the effect coeternal with the cause? It seems like that's very problematic, and it seems like the easiest explanation or the most plausible explanation to how the universe with a first moment in time could come about is to say that agent causation is where we need to look; that it was a personal agent endowed with freedom of the will who can spontaneously exercise causal powers to bring about a new effect. So if that's not true how is naturalism to provide an explanation for that case?
Dr. Carroll: Yeah, I think this is a good question in the sense that this is the kind of issue that tugs at our ability to make sense of these large cosmic questions given our everyday experience with reality. But I will give you a frustrating answer to it by denying your premise. I do not think that if the universe has a first moment in time that means there is any sort of eternal or preexisting conditions or rules or laws or anything like that. It simply means that our best and maybe the correct description of the cosmos is one that had a first moment in time. The question is, can that be self-contained in the sense that I'm using it, which is that if I write down the equations and the conditions and so forth that describe the universe with an earliest moment, am I done? Are there questions that I might have about that universe that cannot be answered by that formalism? And I think there is no obstacle whatsoever to coming up with such models. And so I would simply un-ask the question. I would say, no, there aren’t preexisting or eternal rules. There is the universe and the universe has a first moment and the universe obeys rules during those moments when the universe exists. During those moments when the universe does not exist, there are no moments, there is no time, there are no rules.
Dr. Craig: This question is very closely related to the argument that I gave against the quantum gravity regime's being past eternal. Namely, if the causal conditions that are present there are sufficient for the effect, then the effect would always have been there. But if they're not sufficient, then it becomes incomprehensible why the effect appeared just 13.7 billion years ago. And therefore it seems to me, I argued, that this regime would itself have to have a beginning and come into existence. The contrast with this is, when you have a libertarian agent with free will, he can exist from eternity and then freely decide to produce an effect in time without any antecedent determining conditions. And so in that sense theism provides, I think, an explanatorily superior account of the origin of the universe because it's got the explanatory power that is vested in an agent with libertarian free will.
Question 14: Yes, I'm really afraid I'm going to ask that stupid question, so please excuse me. But I don't really understand how you come up with the probability – or improbability, as you have been saying – of the universe, if it's a universe, when a universe has only begun once? How do you come up with that? Don't you have to have more scores to calculate such a probability?
Dr. Craig: Yeah, now, which argument is this relevant to, in your mind?
Question 14: Before you said there is a universe, and then you have been repeating a lot that it's highly improbable that it just popped out of nothing.
Dr. Craig: Oh, like the finely-tuned universe—okay. I don't think this is a good objection to fine-tuning because what we can do is simply conceptualize a multitude of universes by varying these constants and quantities and seeing what would result. So, for example, the physicist John Barrow gives the following illustration: he says, put a red dot on a piece of paper and let that be our universe. Now, alter slightly one of the constants or quantities. That will make a new universe. If it's life-permitting, make it a red dot. If it's life-prohibiting, make it a blue dot. Now, do it again, and do it again, and do it again, until your sheet of paper is filled with dots. And what you will come up with is a sea of blue with only a couple pin-points of red. It is in that sense that one can say that these finely-tuned universes are enormously improbable. You don't need the universes to actually exist in order to say they're improbable. All you need to do is have this, so to speak, logical space of possible universes described by these different quantities and constants in order to say that finely-tuned worlds are extremely rare.
Dr. Carroll: I think this is a great question because we do have this tendency to speak informally of probabilities and likelihoods and so forth. And even professional cosmologists do this when we talk about the early universe – “That seems improbable, unlikely, unnatural” is the usual term that we use. And sometimes we're just totally wrong about that. As so the example that Dr. Craig just gave about the blue dots and the red dots sadly almost never applies in cosmology because it assumes there is a discrete set of dots that we can color blue or red. Usually in cosmology there is a continuous spectrum of possibilities, and in that case it's much harder to even imagine assigning probabilities consistently. The example I gave, which was then sort of not talked about later, was the expansion rate of the early universe. There was a naïve argument that says it's very improbable. When you look more carefully you realize it's extremely probable. So there's not a definitive answer as to what the correct answer is, but I'm agreeing with your implication that we should be very, very careful when using words like that.
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