This 2/18 post first appeared on the IU Secular Alliance and Philosophical Society blogs.
On February 1, Christian apologist William Lane Craig and philosopher of science Alex Rosenberg debated the relationship between theology and ethics, cosmology, metaphysics, and a range of other topics at Purdue University. And, good golly, they covered a lot. In the interest of deepening this already-broad conversation, I’ll assess the merits of a smattering of their assertions, both scientific and philosophical.
But I’m not going to weigh in on who won. Because I do agree with a fundamental point raised by Rosenberg, not about the debate’s topic but about formal debate itself:
“Philosophy and theology don’t proceed by courtroom-style debate. We’re engaged in a cooperative search for the truth, both theists and atheists, not an adversarial contest for victory. […]
“But that’s the problem with this kind of a debate, and this kind of a format. It doesn’t work. It doesn’t work because what I’d like to be able to do is ask William Lane Craig a question, and listen to his answer, and formulate a reply, and listen to his answer. And then give a view, and listen to his question. Which is the way in which philosophical dialogue proceeds, and which enables us at least to find out where the crucial issues are between us, and how we could mutually agree to adjudicate these matters.“
Rosenberg’s request is simple. He wants to talk to Craig. He wants a real-time back-and-forth, a friendly and open exchange of ideas rather than a stiff gladiatorial combat. If there is a battle of any significance here, it is between all of us and the forces of ignorance and error. Inasmuch as the debate was enlightening, both debaters won; inasmuch as it is was muddled or superficial, both debaters lost. As did we all.
But that battle continues. Just because the debate is presented as highbrow sumo wrestling doesn’t mean we can’t exploit it to open up a richer dialogue. I encourage you to join the discussion, and let me know which of my points you agree or disagree with!
1. God Hypotheses
Craig: “Now there’s only one way I can think of to get a contingent universe from a necessarily existing cause, and that is if the cause is a personal agent who can freely choose to create a contingent reality. It therefore follows that the best explanation of the existence of the contingent universe is a transcendent, personal being. Which is what everybody means by ‘God.’“
Perhaps that’s part of what a lot of people mean by ‘God’. But it’s not everything that is meant by ‘God’. If you learned that this transcendent, personal cause of the universe were ignorant or mad, or that it annihilated itself in the course of making the universe, or that it were a cruel tyrant, it’s unlikely that you would even think of calling this Lovecraftian absurdity ‘God’. Certainly you wouldn’t think that it was your god.
In general, attempts to prove that something has some of the interesting properties you ascribe to your god, although not irrelevant, need to be heavily qualified when there is a great swarm of hypothetical beings that you would never worship but that meet the same requirements. There are thousands of conditions a deity has to meet, above and beyond transcendence and personhood, before it can even begin to approximate the God of the Bible.
Note also that Craig is giving an argument to the best explanation. But the best explanation may not be a very good explanation, if all the options we’ve thought of are unlikely to different degrees. If I ask ten randomly selected people to give their best guess as to the value of -4⁴, I shouldn’t be all that confident that the least unpopular answer is the right answer. The real question is: Would we expect anyone to have thought of the right answer by now? If not, then we may have reason to doubt that the ‘best’ explanation is worth very much. We also have to be wary here of appeals to ignorance; “there’s only one way I can think of…” only matters if everyone else shares your ignorance and if we would strongly expect anyone to have thought of the right answer by now.
2. The Beginning of the Biggening
Craig: “Because we don’t yet have a quantum theory of gravity, we can’t yet provide a physical description of the first split second of the universe. But the Borde-Guth-Vilenkin theorem is independent of any physical description of that moment. Their theorem implies that the quantum vacuum state which may have characterized the early universe cannot be eternal in the past, but must have had an absolute beginning. Even if our universe is just a tiny part of a so-called multiverse composed of many universes, their theorem requires that the multiverse itself must have had an absolute beginning. […]
“But then the inevitable question arises, why did the universe come into being? What brought the universe into existence? There must have been a transcendent cause which brought the universe into being.“
This is almost right, but requires the added stipulation that the multiverse in question be inflationary. I asked Alexander Vilenkin what he thought of Craig’s characterization, and he wrote:
“This is accurate. But note that the theorem assumes that the universe was on average expanding in the past. The conclusion can be avoided if the universe was contracting prior to the expansion. But contracting universes have problems of their own. They are highly unstable, so the contraction is not likely to be followed by an expansion (which we now observe).”
Another possible source of confusion is that Craig’s conclusion — that our universe must have a “transcendent cause” — is not generally endorsed by physicists who do grant that it had a beginning. Vilenkin comments, “I don’t think the cause should necessarily be transcendent.”
What Borde, Guth, and Vilenkin proved is that new, non-inflationary physics is required to “describe the past boundary of the inflating region of spacetime”. Maybe that new physics will have a ‘God’ term; maybe it won’t. But this theorem does not obviously rule out immanent explanations.
3. Immaterial Causes
Craig: “By the very nature of the case, that cause [of the universe] must be a transcendent, immaterial being. Now, there are only two possible things that could fit that description. Either an abstract object, like a number, or an unembodied mind or consciousness.“
Note that Craig gives no argument here that only causally inert abstracta and minds could transcend our universe. Yet he asserts that we not only haven’t come up with such an entity yet, but that such a thing is impossible. This in spite of the many philosophers, from Plato to the present day, who have posited unconscious immaterial causes. Lacking any proof of the impossibility of such things, we must conclude that the argument fails; whereas Craig’s earlier argument-to-the-best-explanation was much more persuasive, though its conclusion was also much weaker.
We have to be especially wary of the fallacy of equivocation here. Craig uses ‘immaterial’ to mean ‘outside the universe’ (like God), but he also uses it to mean ‘not spatially extended’ (like ordinary human mental states). But my mind is in the universe; more specifically, it’s in the United States. My present hunger, for example, isn’t nowhere. (Nor everywhere!) It’s at the particular place where I am. But this means that we don’t know of any minds that are nonphysical in Craig’s sense, and it isn’t obvious that there could be such minds. Likewise, minds as we know them are all temporal; it’s not clear that we have any coherent idea of a thought or sensation existing outside time itself. Insofar as we do have some vague sense of such a mind, surely we might also have a vague sense of branes, Platonic Forms, free-floating Laws, or other world-transcending causes.
4. Anthropic Arguments
Craig: “By far, most of the observable universes in a world ensemble would be worlds in which a single brain fluctuates into existence out of the vacuum and observes its otherwise empty world. Thus, if our world were just a random member of a world ensemble, we ought to be having observations like that. Since we don’t, that strongly disconfirms the world ensemble hypothesis.“
Assessment: Mostly Right
Max Tegmark has proposed that we can explain why our universe seems ‘fine-tuned’ for complex mathematical and biological structure by positing that we’re just a small part of a much larger multiverse of randomly varying mathematical objects. Since we would only expect living things to emerge and notice how nice and friendly their surroundings are in the parts of this giant ‘ensemble’ that make life possible (well, yeah), our universe’s observed hospitability then becomes a lot less surprising.
It’s an interesting idea, but, as Craig suggests, it seems to have some absurd consequences: we should expect all our memories to be an illusion formed out of a chaotic flux. This is because, on Tegmark’s view, most universes are chaotic mishmashes. If I think I’m a brain in a randomly selected universe in Tegmark’s ensemble, then I should expect to be one of the billions of brains randomly and momentarily arising from chaos (complete with fake memories!), rather than one of the rare brains produced by a huge, physically simple chunk of spacetime that lawfully produced me and ancestors like me over millions of years. This is the problem of the Boltzmann Brain.
The easiest response is that we occupy a multitude of relatively simple worlds with just a few randomly varying physical constants (e.g., the fine-structure constant), enough to account for apparent fine-tuning; but that multitude is not so diverse that it has a preponderance of ‘chaotic’ universes generating Boltzmann Brains. This may seem like a somewhat ad-hoc answer, and further serious debate about anthropic reasoning is certainly warranted. Anthropic multiverses like Tegmark’s will have to contend not only with life-selecting mechanisms like Craig’s, but with heavy-element-selecting mechanisms like Lee Smolin’s cosmic evolution.
5. Ancient Miracles
Craig: “There are actually three facts recognized by the majority of historians today which I believe are best explained by the resurrection of Jesus. Fact #1: On the Sunday after his crucifixion, Jesus’ tomb was found empty by a group of his women followers. 2: On separate occasions, different individuals and groups of people saw appearances of Jesus, alive, after his death. And, 3: The original disciples suddenly came to believe in the resurrection of Jesus, despite having every predisposition to the contrary.“
The only evidence Craig cites is N.T. Wright’s claim that these three propositions are “virtually certain”. What Craig doesn’t mention is that Wright is not only a historian, but a Christian apologist and bishop. For that matter, Craig doesn’t note that most New Testament scholars are Christians. (Are we to take it as evidence for the truth of Christianity that a lot of Christians happen to be Christian?)
Now, of course being a Christian doesn’t make it impossible for you to evaluate Christianity in a fair and skeptical way. I believe very strongly that the Earth is round, but that doesn’t mean that I’d be hopelessly biased in a debate with flat-Earthers. Agnosticism does not imply objectivity, and objectivity does not imply agnosticism. If anything, we’d be worried if most New Testament scholars weren’t Christians, since that would suggest that the historical evidence tended to make people less religious than the general populace.
But it’s also worth noting that Christian orthodoxy is not generally considered by historians the only possible objective interpretation of the evidence of the Gospels. And appealing to scholarly consensus here is misleading inasmuch as it has the guise of an appeal to independent authorities, as opposed to authorities who already came into the field accepting Christianity.
As for the claims themselves, before we can even begin to evaluate ancient miracle accounts, we need some training in historical methodology and knowledge of the relevant cultural context. This talk is very informal, and is addressed to a nontheistic audience, but provides a nice introduction to those two topics:
6. The Great Chain of Becausing
Rosenberg: “Many of the arguments that Dr. Craig gave tonight [… rest] on, of course, the Principle of Sufficient Reason, the principle that everything that exists must have a cause.“
Rosenberg: “We know that alpha particles come into existence for no reason at all every moment in this room. Why should we assume that the universe is any different? Why should we assume that purely quantum-mechanical fluctuations — symmetry breaking, which we understand is the explanation for why there’s matter in the universe and not antimatter — why this process which produces the characteristic features of our universe and does so without there being a cause for its happening one way or the other, why the symmetry gets broken one way or the other, couldn’t be the nature of reality as far back as we can possibly dig in cosmology?“
Craig does not appeal to a principle as strong as ‘everything has a sufficient reason/cause/explanation independent of itself’. Were he to do so, his arguments for God would backfire, since God would then need to be caused or explained in its own right. Instead, Craig claims (a) that physical events and things always require an explanation (and the universe, of course, is physical), and (b) that contingent things always require an explanation. Rosenberg questions (a), and we could also question (b), or ask how we know that anything is really contingent. But it’s important not to conflate these three claims.
It seems that just as Craig is arguing from ’every physical event has a cause’ to ‘the universe must have a cause’, Rosenberg is arguing from ‘many physical events lack a cause’ to ‘the universe lacks a cause’. Neither of these inferences seems very strong to me. (EDIT: Rosenberg tells me that he rather “is arguing from ‘many physical events lack a cause’ to ‘[it’s] possible that the universe lacks a cause.[‘]”)
Vilenkin suggests, in correspondence:
“This is not very clear, but it seems that what he [Rosenberg] is referring to is the creation of closed universes from ‘nothing’. The possibility of such a process is indeed suggested by quantum cosmology, but the word ‘nothing’ should be interpreted with care. Here, it is taken to mean a state with no matter and no classical space and time. But the origin of the universe is described by the laws of physics, so the laws are assumed to be ‘there’ as an input. Mr. Craig may argue that the laws must be provided by God. I am not sure this explains anything; we could just as well say that the laws have always been ‘there’. However, in fairness I should admit that so far physics offered no explanation for the laws. Why these laws and not some other? Why any laws at all?”
Physics graduate student Jeffrey Eldred provides a defense of Rosenberg’s general approach, though he notes that Rosenberg is mistaken in thinking that physicists look to spontaneous symmetry breaking to explain the matter-antimatter disparity:
“Rosenberg[‘s claim] ‘…quantum-mechanical fluctuations, symmetry breaking, which we understand is the explanation for why there’s matter in the universe and not anti-matter…’ is not generally accepted by physicists and cosmologists. Physicists already have experimental confirmation of matter-antimatter asymmetry in the properties of quarks, and there are experiments underway expecting to find the remainder of the asymmetry. […] I don’t know what Rosenberg was thinking about. Perhaps he was jumping the gun and […] looking to the theories that would explain matter-antimatter asymmetry in the event we didn’t find it in the neutrino sector, or maybe he was uncritically endorsing remarks reportedly made by Einstein. […]
“Spontaneous symmetry-breaking is the idea that an unstable symmetric system will be forced to break the symmetry in an arbitrary direction. Classically if you balance a perfectly [cylindrically] symmetric, perfectly sharp pencil perfectly on its point [then] it will never fall over. Quantum-mechanically, random fluctuations in the particles that make it up would force it to become slightly asymmetric and then cause it to settle into a stable asymmetric state (lying on the table pointing in a random direction). Whatever your interpretation is, the way the symmetry will break cannot be known from our perspective and the consequences of those fluctuations can be lasting. […]
“Inflationary theories are supported in part by Cosmic Microwave Background evidence that shows the distribution of matter in the universe fits the model of quantum fluctuations between close particles and then subsequent inflation. Inflation theories can explain in a similar way any parameter of the universe which depends on the distribution of matter, the mechanism of inflation, or could vary slowly over scales larger than our universe. The original [arrangement] of matter could be empty but then spontaneous symmetry breaking of the unstable vacuum state could cause it to become populated with matter.
“I’m not sure […] how Rosenberg is linking this to other parameters of the universe such as the gravitational constant or if he is even trying to explain them. Is he assuming that there is a different but analogous process for those parameters or is he saying that they are created by the same mechanism? Here’s how they could be created by the same mechanism. Let’s say for instance the gravitational constant varied over space in the very early universe (ie the multiverse) and subsequently inflation took place in a very small region of that space which would eventually get inflated into our universe. That would mean our universe would have an effectively constant gravitational constant because the gravitational constant wouldn’t vary much in such a small original space, and our gravitational constant could be picked effectively at random from the true possible variation in the gravitational constant if there was nothing special about the space that would become our universe. We don’t know that to be true about the gravitational constant but if inflation is right than we might never […] know if it is true about the gravitational constant or any other parameter. We might try to analyze if our universe is a typical random (or typical anthropically selected) universe from the possibilities, but we might not even be able to know what a typical universe is since we can’t observe any outside our own universe.”
7. Anthropics Revisited
Rosenberg: “To begin with, this is terrible carbon chauvinism. If these constants had been slightly different, maybe there would be intelligent life in the universe that’s germanium-based or silicon-based.“
In fact, silicon- or germanium-based life may very well exist in our universe. But, as Craig correctly notes, the sorts of radical tinkerings that fine-tuning arguments appeal to would generally make all stable atoms impossible, not just carbon. So, although the suggestion that life might be possible in universes with very different physical constants would be a powerful anthropic rejoinder, a lot of work will need to be done to make it credible. Until then, the best anthropic arguments will appeal to some sort of multiverse.
8. Space Opera
Rosenberg: “Scientology, that claims 8 million adherents throughout the world, tells us that 75,000,000 years ago somebody named Zeno brought spaceships to Earth that look like DC-8s.“
The guy’s name was Xenu.
… Otherwise, yeah, that’s right.
(Though it’s worth noting that while Scientology claims 8 million adherents, the actual numbers are smaller by an order of magnitude or two.)
(Also, no way would Zeno have finished that trip.)
Rosenberg: “Think about this: 53 of the first 62 DNA exonerations of people who turned out to be innocent of charges of capital crimes in the United States were convicted on eye-witness testimony. We know from cognitive, social science how unreliable eye-witness testimony is today. Why should we suppose that eye-witness testimony from 33 AD is any more reliable? This, as an argument for God’s existence, seems to me to be bizarre.“
Assessment: Mostly Right
This is a very important point. Wells, Memon, and Penrod note: “Analyses of DNA exoneration cases since 1992 reveal that mistaken eyewitness identiﬁcation was involved in the vast majority of these convictions, accounting for more convictions of innocent people than all other factors combined.”
What’s potentially misleading here is the suggestion that we have eye-witness testimony of any event from Jesus’ life. As Rosenberg later notes, the Gospels are generally dated to 40-60 years after Jesus’ death, and none of them even claims to be an eye-witness account.
10. The Problem of Evil
Rosenberg: “Logically speaking, if God is omniscient, and God is omnipotent, and God is truly benevolent, has a totally good will and would never will anything but for the best, then the existence of suffering on our planet — human suffering and natural suffering, of other animals, for example — is something that needs desperately to be explained. And we’ve had over the course of 400 or 500 years of wrestling with this problem the Free Will defense, and the mystery-mongering […] defense, and nobody has managed to provide a satisfactory explanation. And I insist that the problem is logical. And Dr. Craig needs to tell us exactly how an omnipotent god, and an entirely benevolent god, had to have the Holocaust, in order to produce the good outcome, whatever it might be, that he intends for our ultimate providence. […] In all honesty, if Dr. Craig could provide me with any way of a logical, coherent account that could reconcile the evident fact of the horrors of human and infrahuman life on this planet over the last 3.5 billion years, with the existence of a benevolent, omnipotent agent, then I will turn Christian.“
Rosenberg’s argument here is perplexing. His actual points are perfectly fine — as inductive, probabilistic arguments. Many of Craig’s own arguments are probabilistic. But Rosenberg repeatedly uses the word ‘logical’, which Craig takes to refer to ‘the logical problem of evil’, the attempt to deductively prove the impossibility of God’s coexisting with evil. Either Rosenberg is misrepresenting the force of his own arguments, or there’s a serious communication gap between him and Craig.
If Rosenberg is happy to settle for induction, then that would explain why he repeatedly demands a theistic explanation for atrocities like the Bubonic Plague and the Holocaust. It doesn’t make any sense to demand explanations for logical contradictions like square circles; we can simply note that they’re impossible and move on. But it does make sense to demand explanations if you just think that God is overwhelmingly unlikely, rather than impossible.
This miscommunication is doubly unfortunate because it leads Rosenberg and Craig to talk past each other in terms of the burden of proof: Rosenberg repeatedly demands that Craig explain how a good God could have allowed evil, while Craig repeatedly demands that Rosenberg prove the impossibility of there being some good reason we haven’t yet figured out. When what’s being disputed is unclear, the burden of proof will be correspondingly unclear.
That said, there might be some interesting deductive arguments against the coexistence of evil with certain concepts of a benevolent God. For instance, here’s one I came up with:
1. God is perfect. Among other things, this means that God is perfectly benevolent and perfectly knowledgeable.
2. God is the sole creator of our universe.
3. If God is perfect, then in a situation in which only God existed, there would be no shortcomings.
4. If a situation has no shortcomings, then it cannot be improved upon.
5. So God’s creation of our universe could not have been an improvement. (from 1, 2, 3, 4)
6. A perfectly benevolent being will not knowingly bring about a situation that risks producing evil, if doing so could not improve upon the prior situation.
7. Creating our universe risked producing evil.
8. So God is not perfectly benevolent. (from 1, 5, 6, 7)
9. Contradiction. (from 1, 8)
This argument is valid, but some of its premises may be counter-intuitive. In particular, some people may want to insist that God’s creation of free agents was an improvement upon the status quo; but it’s hard to articulate how that could be so without watering down 1. Alternatively, some may want to insist that benevolence is not about improving scenarios (denying 6). But this just doesn’t seem right. Benevolence may not only consist in improving reality, but that’s surely at least one important factor; all else being equal, it’s better for the world to be better, to have a higher good-to-evil ratio! And, again, given God’s perfection, it’s hard to articulate what advantage could outweigh the colossal suffering (or risk-of-suffering) God engendered.
But I digress. I just wanted to illustrate what a deductive argument from evil might look like. Rosenberg himself doesn’t clearly formulate one.
Craig: “But if God does not exist, then I think metaphysical naturalism is true. Metaphysical naturalism doesn’t follow from epistemological naturalism, but it does follow from atheism. The most plausible form of atheism is, I think, metaphysical naturalism. But there are all those absurd consequences that result from that that I describe.“
By ‘theism’ Craig seems to mean the belief in a necessary, uncaused, simple, immaterial person who existed outside of spacetime, freely created the universe, and is identical to goodness. But he also seems to treat ‘atheism’ here as just the negation of theism; it’s any view on which theism is false. But then there are numerous monotheisms and polytheisms that qualify as ‘atheistic’ in the relevant sense, since they deny at least one of the properties Craig ascribes to God (e.g., simplicity, or necessity, or benevolence).
There’s also some ambiguity in Craig’s claim that “metaphysical naturalism[…] does follow from atheism“. Polytheistic doctrines surely do not count as naturalisms. For that matter, we intuit that werewolves, sorcery, and astrological influences are ‘supernatural;’ they violate metaphysical naturalism. But we don’t have to believe in Craig’s deity to consistently believe in magic. Either Craig is committing a false dilemma fallacy with respect to theism and atheism, or he’s committing a false dilemma fallacy with respect to naturalism and non-naturalism.
So let’s reconstruct a more charitable version of the argument. I don’t think Craig means to say that metaphysical non-naturalism logically entails his version of theism. Rather, he takes it as self-evident that naturalism is false — because he (a) equates naturalism with physicalism, and (b) assumes that human thought, perception, and language cannot possibly be physical. The former, (a), is very nonstandard, and constitutes a third false dilemma. But let’s grant it for the moment. Craig’s argument then is, I think, that the truth of (b) does not entail theism, but rather that theism is the only serious contender for a satisfactory explanation of (b). Craig’s issue with atheism, then, is that it denies the best explanation for the data; and he thinks this is only intellectually sustainable if one also denies the (unphysical) data themselves.
As such, these are the points Craig needs to focus on in order to make his case:
(1) Show that seemingly non-physical things, like thoughts and words, cannot be explained by or analyzed into physical processes (e.g., brain computations). This gets rid of reductive physicalism.
(2) Establish that eliminative treatments of thoughts and words are not only counter-intuitive or silly-sounding, but actually false. This gets rid of eliminative physicalism, including Rosenberg’s view.
(3) Establish that all possible (or plausible) metaphysical naturalisms must be physicalistic. Given 1 and 2, this gets rid of naturalism.
(4) Establish that all possible (or plausible) metaphysically non-naturalist views must appeal to Craig’s version of the God hypothesis.
And in the course of the above, Craig must not merely establish that his version of theism is the best (i.e., least terrible) explanation, but that it’s probably right.
That may sound like a lot, but it’s only fair that Craig start to seriously fill in the details in his view, given how many arguments he typically demands that his debate opponents make!
12. Biblical Language
Rosenberg: “And all of [the New Testament scholars] tell us that it was written by people who were illiterate. […] And of course the Aramaic in which they [the Gospels] were written was completely lost, and all the extant New Testaments are in Greek.“
The Bible was written by illiterate people? A miracle!
OK, I think this is a scrambled version of what’s supposed to be the claim that because the Gospel writers were literate, they couldn’t have been the (mostly illiterate) apostles. But this argument is a bit superfluous, since the Gospels themselves make no claim to be written by apostles.
The second claim is also wrong. As Craig points out, the New Testament was originally written in Greek. This does suggest a cultural divide between the New Testament writers and the early Aramaic/Hebrew-speaking followers of Jesus, but such a divide doesn’t require that the texts be mistranslated.
13. Quantum Indeterminacy
Rosenberg: “Now, if every event has to has a cause, if everything that comes into existence has to have a cause of its coming into existence, then there’s got to be some difference between the two atoms in virtue of which one of them emitted an alpha particle and the other didn’t. But quantum mechanics tells us, and all the experimental evidence which confirms it to twelve decimal places tells us, there is no difference. End of story. There is an event without a cause. […]
“This is not an issue about the interpretation of quantum mechanics. I happen to think that among the interpretations of quantum mechanics, some of the deterministic ones are more plausible than others. This is a matter of experimental physics. This is a matter of a fact about the nature of reality. And it also seems to me clear that insofar as we have here good evidence that things can happen with no cause at all, it follows that therefore the universe can come into existence with no cause at all. And, indeed, that’s what the best guesses of contemporary physical theorists is.“
Rosenberg is simply wrong here. The standard, early-20th-century interpretations of the data and formalisms of quantum mechanics were indeed indeterministic. But these ‘Objective Collapse’ interpretations have become increasingly unpopular, because they posit a fundamental discontinuity in the laws of nature, a sharp point where the laws of microphysics abruptly give way to the laws of macrophysics. This is not only inelegant, but empirically implausible, since we have yet to identify any well-defined criterion for circumstances in which collapse does or doesn’t occur. (For instance, some Collapse theorists suggest that wave functions collapse whenever a ‘measurement’ occurs. But what, in physics, counts as a ‘measurement’? There is no rigorous definition.)
As a result, alternative interpretations of quantum mechanics have become increasingly popular. And a primary distinction between the older and newer interpretations is that the newer ones are deterministic. Everett-style (‘Many Worlds’) interpretations explain the apparent indeterminism anthropically, by suggesting that the observer somehow becomes cut off from an equally real but hidden portion of the wave function. And de-Broglie-style (‘Hidden Variables’) interpretations explain the apparent indeterminism by positing an unobservable difference between the initial state of the two systems, the precise position of the particle.
Both of these types of interpretations have their problems, and it will take a great deal of argument to compare their flaws and merits to those of the Collapse school. But the basic reason Rosenberg is mistaken isn’t that he favors Collapse over its rivals; it’s that he falsely asserts that Collapse is a fact, an observation, a truth of experience. It isn’t. It’s an unverified and unfalsified way of construing the data. The claim that smoke detectors wouldn’t work if a deterministic model like Bohmian Mechanics were correct falls somewhere between the speculative and the absurd.
Eldred suggested to me that we fortify Rosenberg’s position with an argument that depends less on choice of interpretation, say, “If no experiment can determine whether events need causes [then] no experiment can determine whether the universe needs a cause.” I’m not sure this argument works either, but at least its premise is less speculative, given that the major interpretations of quantum mechanics are empirically equivalent. (EDIT: After talking with Rosenberg, I believe he prefers this version of the argument.)
Craig and Rosenberg both raise a lot of difficult issues, and some of them I haven’t even touched on — like the projects of naturalizing mathematics, morality, and meaning. But this should be plenty to sift through for the moment. If you have any questions, comments, or concerns, let me know! I welcome any opportunities to have my current beliefs upset and overturned.