Sean Carroll: Does the Universe Need God? [link]

by Dreaded_Anomaly7 min read23rd Mar 201122 comments

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Does the Universe Need God? (essay by Sean Carroll)

In this essay, Sean Carroll:

  • Dissolves the problem of "creation from nothing":

    A provocative way of characterizing these beginning cosmologies is to say that "the universe was created from nothing." Much debate has gone into deciding what this claim is supposed to mean. Unfortunately, it is a fairly misleading natural-language translation of a concept that is not completely well-defined even at the technical level. Terms that are imprecisely defined include "universe," "created," "from," and "nothing." (We can argue about "was.")

    The problem with "creation from nothing" is that it conjures an image of a pre-existing "nothingness" out of which the universe spontaneously appeared – not at all what is actually involved in this idea. Partly this is because, as human beings embedded in a universe with an arrow of time, we can't help but try to explain events in terms of earlier events, even when the event we are trying to explain is explicitly stated to be the earliest one. It would be more accurate to characterize these models by saying "there was a time such that there was no earlier time."

    To make sense of this, it is helpful to think of the present state of the universe and work backwards, rather than succumbing to the temptation to place our imaginations "before" the universe came into being. The beginning cosmologies posit that our mental journey backwards in time will ultimately reach a point past which the concept of "time" is no longer applicable. Alternatively, imagine a universe that collapsed into a Big Crunch, so that there was a future end point to time. We aren't tempted to say that such a universe "transformed into nothing"; it simply has a final moment of its existence. What actually happens at such a boundary point depends, of course, on the correct quantum theory of gravity.

    The important point is that we can easily imagine self-contained descriptions of the universe that have an earliest moment of time. There is no logical or metaphysical obstacle to completing the conventional temporal history of the universe by including an atemporal boundary condition at the beginning. Together with the successful post-Big-Bang cosmological model already in our possession, that would constitute a consistent and self-contained description of the history of the universe.

    Nothing in the fact that there is a first moment of time, in other words, necessitates that an external something is required to bring the universe about at that moment. As Hawking put it in a celebrated passage:

    So long as the universe had a beginning, we could suppose it had a creator. But if the universe is really self-contained, having no boundary or edge, it would have neither beginning nor end, it would simply be. What place, then, for a creator?
  • Uses Bayesian reasoning to judge possible explanations:

    Nevertheless, for the sake of playing along, let's imagine that intelligent life only arises under a very restrictive set of circumstances. Following Swinburne, we can cast the remaining choices in terms of Bayesian probability. The basic idea is simple: we assign some prior probability – before we take into account what we actually know about the universe – to each of the three remaining scenarios. Then we multiply that prior probability by the probability that intelligent life would arise in that particular model. The result is proportional to the probability that the model is correct, given that intelligent life exists.[17] Thus, for option #2 (a single universe, no supernatural intervention), we might put the prior probability at a relatively high value by virtue of its simplicity, but the probability of life arising (we are imagining) is extremely small, so much so that this model could be considered unlikely in comparison with the other two.

    We are left with option #3, a "multiverse" with different conditions in different regions (traditionally called "universes" even if they spatially connected), and #4, a single universe with parameters chosen by God to allow for the eventual appearance of life. In either case we can make a plausible argument that the probability of life arising is considerable. All of the heavy lifting, therefore, comes down to our prior probabilities – our judgments about how a priori likely such a cosmological scenario is. Sadly, prior probabilities are notoriously contentious objects.

    I will consider more carefully the status of the "God hypothesis," and its corresponding prior probability, in the final section. For now, let's take a look at the multiverse.
  • Correctly describes parsimony in terms of Kolmogorov complexity:

    What prior likelihood should we assign to such a scenario? One popular objection to the multiverse is that it is highly non-parsimonious; is it really worth invoking an enormous number of universes just to account for a few physical parameters? As Swinburne says:

    To postulate a trillion trillion other universes, rather than one God in order to explain the orderliness of our universe, seems the height of irrationality.

    That might be true, even with the hyperbole, if what one was postulating were simply "a trillion trillion other universes." But that is a mischaracterization of what is involved. What one postulates are not universes, but laws of physics. Given inflation and the string theory landscape (or other equivalent dynamical mechanisms), a multiverse happens, whether you like it or not.

    This is an important point that bears emphasizing. All else being equal, a simpler scientific theory is preferred over a more complicated one. But how do we judge simplicity? It certainly doesn't mean "the sets involved in the mathematical description of the theory contain the smallest possible number of elements." In the Newtonian clockwork universe, every cubic centimeter contains an infinite number of points, and space contains an infinite number of cubic centimeters, all of which persist for an infinite number of separate moments each second, over an infinite number of seconds. Nobody ever claimed that all these infinities were a strike against the theory. Indeed, in an open universe described by general relativity, space extends infinitely far, and lasts infinitely long into the future; again, these features are not typically seen as fatal flaws. It is only when space extends without limit and conditions change from place to place, representing separate "universes," that people grow uncomfortable. In quantum mechanics, any particular system is potentially described by an infinite number of distinct wave functions; again, it is only when different branches of such a wave function are labeled as "universes" that one starts to hear objections, even if the mathematical description of the wave function itself hasn't grown any more complicated.

    A scientific theory consists of some formal (typically mathematical) structure, as well as an "interpretation" that matches that structure onto the world we observe. The structure is a statement about patterns that are exhibited among the various objects in the theory. The simplicity of a theory is a statement about how compactly we can describe the formal structure (the Kolmogorov complexity), not how many elements it contains. The set of real numbers consisting of "eleven, and thirteen times the square root of two, and pi to the twenty-eighth power, and all prime numbers between 4,982 and 34,950" is a more complicated set than "the integers," even though the latter set contains an infinitely larger number of elements. The physics of a universe containing 1088 particles that all belong to just a handful of types, each particle behaving precisely according to the characteristics of its type, is much simpler than that of a universe containing only a thousand particles, each behaving completely differently.
  • Discusses "meta-explanatory accounts":

    For convenience I am brutally lumping together quite different arguments, but hopefully the underlying point of similarity is clear. These ideas all arise from a conviction that, in various contexts, it is insufficient to fully understand what happens; we must also provide an explanation for why it happens – what might be called a "meta-explanatory" account.

    It can be difficult to respond to this kind of argument. Not because the arguments are especially persuasive, but because the ultimate answer to "We need to understand why the universe exists/continues to exist/exhibits regularities/came to be" is essentially "No we don't." That is unlikely to be considered a worthwhile comeback to anyone who was persuaded by the need for a meta-explanatory understanding in the first place.

    Granted, it is always nice to be able to provide reasons why something is the case. Most scientists, however, suspect that the search for ultimate explanations eventually terminates in some final theory of the world, along with the phrase "and that's just how it is." It is certainly conceivable that the ultimate explanation is to be found in God; but a compelling argument to that effect would consist of a demonstration that God provides a better explanation (for whatever reason) than a purely materialist picture, not an a priori insistence that a purely materialist picture is unsatisfying.

    Why are some people so convinced of the need for a meta-explanatory account, while others are perfectly happy without one? I would suggest that the impetus to provide such an account comes from our experiences within the world, while the suspicion that there is no need comes from treating the entire universe as something unique, something for which a different set of standards is appropriate.

    ...

    States of affairs only require an explanation if we have some contrary expectation, some reason to be surprised that they hold. Is there any reason to be surprised that the universe exists, continues to exist, or exhibits regularities? When it comes to the universe, we don't have any broader context in which to develop expectations. As far as we know, it may simply exist and evolve according to the laws of physics. If we knew that it was one element of a large ensemble of universes, we might have reason to think otherwise, but we don't. (I'm using "universe" here to mean the totality of existence, so what would be called the "multiverse" if that's what we lived in.)

    ...

    Likewise for the universe. There is no reason, within anything we currently understand about the ultimate structure of reality, to think of the existence and persistence and regularity of the universe as things that require external explanation. Indeed, for most scientists, adding on another layer of metaphysical structure in order to purportedly explain these nomological facts is an unnecessary complication. This brings us to the status of God as a scientific hypothesis.
  • Points out the theory-saving in and the predictive issues of God as a hypothesis:

    Similarly, the apparent precision of the God hypothesis evaporates when it comes to connecting to the messy workings of reality. To put it crudely, God is not described in equations, as are other theories of fundamental physics. Consequently, it is difficult or impossible to make predictions. Instead, one looks at what has already been discovered, and agrees that that's the way God would have done it. Theistic evolutionists argue that God uses natural selection to develop life on Earth; but religious thinkers before Darwin were unable to predict that such a mechanism would be God's preferred choice.

    ...

    This is a venerable problem, reaching far beyond natural theology. In numerous ways, the world around us is more like what we would expect from a dysteleological set of uncaring laws of nature than from a higher power with an interest in our welfare. As another thought experiment, imagine a hypothetical world in which there was no evil, people were invariably kind, fewer natural disasters occurred, and virtue was always rewarded. Would inhabitants of that world consider these features to be evidence against the existence of God? If not, why don't we consider the contrary conditions to be such evidence? 
  • And more!

See also his blog entry for more discussion of the essay.

Edit: added the bullet point about "meta-explanatory accounts."

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*Discusses "meta-explanatory accounts":

Carroll argues that scientists are not obligated to provide a satisfying answer to "Why does something exist instead of nothing?", and shows some ways , but he does not disolve the question. The question, and related questions, remain interesting, and the answers if we can find it may still be useful.

To me this particular question was always absolutely uninteresting. What precisely dou you find interesting here?

If dissolving means explaining why some people find the question intriguing then there may be multiple dissolutions, each valid for some subset of people. E.g.

  • Belief that the broader its scope, the more important the question is. Questions about everything are broadest, thus most important and worth answering.
  • Instrumental value of this question (and particular answers to it) for justification of various arbitrary philosophies and religions.
  • Belief that any grammatically correct question has a sensible answer, perhaps a unique one. (Failing to recognise the limits of language.)
  • Belief that any fact should have a cause in some sense. (Failing to recognise the limits of intuitions.)

No, he makes a stronger claim than that.

States of affairs only require an explanation if we have some contrary expectation, some reason to be surprised that they hold.
...
There is no reason, within anything we currently understand about the ultimate structure of reality, to think of the existence and persistence and regularity of the universe as things that require external explanation.

No, he makes a stronger claim than that.

States of affairs only require an explanation if we have some contrary expectation, some reason to be surprised that they hold.

That claim is just an unsupported assertion.

Also, I take issue with the concept of a state of affairs requiring an explanation. Certainly this requirement is not a property of the state of affairs, it is rather a property of a mind that is considering the state of affairs. But what does it mean even then? That a mind with this requirement refuses to beleive the state of affairs without the explanation? That a mind that does believe the state affairs but lacks an explanination will compulsively search for an explanation? Well, fine, you can reject requiring an explanation under that sort of definition, and still be interested in an explanation.

We have no prior reason to expect that "nothing" would be a viable alternative to "something." Trying to explain "why existence" is pointless; existence is, inherently. Explaining how existence works is the useful and meaningful goal.

Are you saying something like the following?

There must be some true descriptions of a reality, i.e. actualized rules or meta-rules or meta-...rules, because just as "there are no applicable rules" is a meta-rule, "there are no rules or meta-rules or meta-meta-rules or meta-...rules" would be a meta-(meta-[meta-{meta-...}])rule.

So by counterfactually assuming no low-level rules while being indifferent to the number of (meta-[meta-{meta-...}])rules, we arrived at an infinity of (meta-[meta-{meta-...}])rules, one per level of meta after the lowest/first level: "There are no actualized rules, there is only one meta-rule, there is only one meta-meta-rule...there is only one (meta-[meta-{meta-...}])rule".

If there were any other lowest/first level rule, it would be possible to make a different meta-rule describing the lower rule and thereby form the base of what could only be a different infinite meta-tower than that described above as the result of not having low-level rules. In any case, that would be at least one base-level rule.

Therefore, the question "Why are there some true actualized (meta-[meta-{meta-...}])rules?" is ill-formed because it logically could not be otherwise.

Finally, if the question "why is there X rather than not X?" is ill-formed because the counterfactual of assuming (not X) led to a contradiction, then not (not X) i.e. X. So: not "why is it the case that there are at least some (meta-[meta-{meta-...}])rules rather than none?", rather, "there are at least some (meta-[meta-{meta-...}])rules."

Yes, that is what I'm saying. "Nothing" means no space, no time, no energy, no particles, no fields, no interactions... not even any "meta-rules," as you put it. Existence is fundamentally the context of everything, regardless of at how many levels we can describe it, or how many forms the rules could or do take. When we discuss phenomena within the context, it can make sense to say "why is there X rather than not X (or Y, or Z...)", but it doesn't make sense to discuss the context itself in that way.

it doesn't make sense to discuss the context itself in that way.

As I think of it, it does make sense to talk about the wider context of the rules, which are the meta-rules, but it does not make sense to demand a context that cannot itself be described within a wider context.

(If a (meta-[meta-{meta-...}])ruleset had a horizontal slice of the meta-tower identical to the other immediately higher and lower slices, then it would provide its own context. Somehow the rules and meta-rules would have to be identical, but it would still have a context, it just wouldn't be a different context. I'm not sure this is possible, but that "possible" world isn't ours anyway. If it were, the rules would be the meta-rules too, and we wouldn't have to look deeper.

I strongly doubt the tower can repeat, e.g. with rules identical to meta-meta-rules, unless they are also equal to the meta-rules and every other level.

The "tower" with rules on the bottom, meta-rules above that, etc. is either repeating or non-repeating, but I don't see how it could have a limited number of floors.)

Regardless, if the rules/first floor is empty (i.e. there are no rules by which anything exists) then the meta-rules/second floor has an occupant (i.e. "there are no rules by which anything exists") so the meta-tower isn't empty.

We have no prior reason to expect that "nothing" would be a viable alternative to "something."

I absolutely agree with this. To establish that "non-existence" is exclusively opposed to "existence" requires a careful analysis of the nature of existence.

Can anybody point to work along these lines? I am actively researching the topic.

Trying to explain "why existence" is pointless; existence is, inherently.

I'm not sure how you mean this. By "why existence", do you mean something like the "purpose of existence"?

Explaining how existence works is the useful and meaningful goal.

I agree. I think that this topic ties directly to epistemology; explaining the nature of existence will help to explain the nature of knowledge.

I'm not sure how you mean this. By "why existence", do you mean something like the "purpose of existence"?

I mean in the sense "why does existence exist?". It's really an inappropriate question, despite our ability to phrase it in what seems like a grammatically/linguistically correct way.

I mean in the sense "why does existence exist?".

Then I agree that this question is probably poorly formed. Certainly it isn't obvious to me that it is a meaningful or useful question.

I'm not sure why we have been down-voted for these comments. I suspect that it is because questioning existence in this way appears to challenge the "objective existence" aspects of scientific realism. (Down-voters please comment if I'm wrong.)

I'm not sure why we have been down-voted for these comments. I suspect that it is because questioning existence in this way appears to challenge the "objective existence" aspects of scientific realism. (Down-voters please comment if I'm wrong.)

I have had a fair amount of downvoting on this topic, with very little explanation. It's somewhat frustrating.

sigh this is an unfortunate reply

First, the point made about no time existing prior to the Big Bang applies just as readily to the Standard Model as it does to Hawking's newer model (which fudges math to create imaginary time and a "no boundary" version of the beginning). This new version accomplished nothing (no pun intended), because under any model it is nonsense to ask "What existed before time?" (because "before" is a temporal term, obviously). However, the question of WHY is there a universe at all? (i.e. what is the REASON?) is a perfectly fair question that should not be avoided (and is not temporally-based).

You said, "We have no prior reason to expect that 'nothing' would be a viable alternative to 'something.'" Of course we do! Our experience ONE-HUNDRED PERCENT of the time contradicts this statement.

You said, "Trying to explain 'why existence' is pointless; existence is, inherently." You're committing the taxicab fallacy. You can't just dismiss the causal principle at the point you're "ready to get out." If anything in your daily life happened out of the ordinary (like your car changed colors or someone threw a rock through your window), you would look for a sufficient REASON (because there IS one).

Finally, you said, "Explaining how existence works is the useful and meaningful goal." Um, this is useful and meaningful (I agree), but we are only able to accomplish this using a little thing called the "Law of Causality." So you're willing to use the causal principle for EVERYTHING all the way back to the beginning, but then you choose to stick your head in the sand?

Once again...unfortunate.

Did you actually read the essay?

In Aristotle's Metaphysics, he suggested the need for an "unmoved mover" to explain the motion of ordinary objects. That makes sense in the context of Aristotle's physics, which was fundamentally teleological: objects tended toward their natural place, which is where they wanted to stay. How, then, to account for all the motion we find everywhere around us? But subsequent developments in physics – conservation of momentum, Newton's laws of motion – changed the context in which such a question might be asked. Now we know that objects that are moving freely continue to move along a uniform trajectory, without anything moving them. Why? Because that's what objects do. It's often convenient, in the context of everyday life, for us to refer to this or that event as having some particular cause. But this is just shorthand for what's really going on, namely: things are obeying the laws of physics.

Likewise for the universe. There is no reason, within anything we currently understand about the ultimate structure of reality, to think of the existence and persistence and regularity of the universe as things that require external explanation. Indeed, for most scientists, adding on another layer of metaphysical structure in order to purportedly explain these nomological facts is an unnecessary complication.

However fundamental you think the "causal principle" may be, modern physics is not done that way.

You're making statements about events or phenomena that happen within the universe, and then taking a gigantic, unfounded leap to apply the same principles to the universe itself. How could we possibly have a prior reason to expect the absence of all existence? Not the existence of some specific thing, but existence, in the broadest sense.

States of affairs only require an explanation if we have some contrary expectation, some reason to be surprised that they hold.

That's certainly a requirement for that state of affairs being evidence for anything, but it's not so clear for requiring an explanation, mostly because there seems to be no rigorous sense of what "requiring an explanation" means in the first place.

there seems to be no rigorous sense of what "requiring an explanation" means in the first place.

"Requiring an explanation" means "low probability". An "explanation" is a datum such that conditioning on it makes the probability high.

You can think of probability as an "inverse surprise score" that you try to keep as high as possible. (And of course, there's no cheating.)

negative surprise log score?

So "requiring an explanation" means "strong evidence the hypothesis space has not yet been searched for"? That seems plausible. Is this your on the spot suggestion or has it been discussed before?

On cosmology, I found Theory of Nothing quite interesting even if a whole bunch of it has been rightfully replaced by SL5 decision theory / cosmology concepts. It basically summarizes the kind of cosmology that was going on on the Everything mailing list before it got quiet. It's probably the best place to go if you don't have the luxury of hanging out with certain people in the Visiting Fellows program at SIAI for a year. The idea that an infinite ensemble, like the Library of Babel, has no information content (as seen from the 'outside), dissolved a few confusions for me (though of course many are left) and gave me something of a momentary experience of sunyata. I don't contemplate that thought much anymore for fear that I will 'use up' the novelty of sunyata.

Tsk-tsk. He rejects the hypothesis of a single universe because he fails to consider the anthropic principle.