The BGV Theorem Does Not Mean What You Think it Means

I’ve addressed the use and misuse of the Borde-Guth-Vilenkin (BGV) Theorem a number of times in the past (The Misquoting WLC, The Eternally Inflated (Multiverse and WLC) and Multiholes in WLC’s Physics Arguments).

The apologetic argument goes a bit like this:  Atheists are terrified by the idea the universe must have begun, because if the universe has not been in existence forever, something must have created it.  The BGV Theorem says that inflation must have had a beginning, so the universe has a beginning, therefore the universe has a creator.  Therefore god.  (Much leaping around fisting the air and yelling “OOH-ya” and “who da man”.)

To be brutally frank, Vilenkin (one of the authors of the theorem) seriously did not help when he wrote:

It is said that an argument is what convinces reasonable men and a proof is what it takes to convince even an unreasonable man. With the proof now in place, cosmologists can no longer hide behind the possibility of a past-eternal universe. There is no escape: they have to face the problem of a cosmic beginning.

Admittedly, he did write a couple of paragraphs later:

Theologians have often welcomed any evidence for the beginning of the universe, regarding it as evidence for the existence of God… So what do we make of a proof that the beginning is unavoidable? Is it a proof of the existence of God? This view would be far too simplistic. Anyone who attempts to understand the origin of the universe should be prepared to address its logical paradoxes. In this regard, the theorem that I proved with my colleagues does not give much of an advantage to the theologian over the scientist. As evidenced by Jinasena’s remarks earlier in this chapter, religion is not immune to the paradoxes of Creation.

But the damage had already been done, there was a paragraph begging to be cherry picked by apologists and they went to town.  (A search on “There is no escape: they have to face the problem of a cosmic beginning” brings up page after page of apologetic nonsense.

As an aside to very interesting video on a universe from ‘nothing’, Vilenkin makes a very clear comment to the effect that the BGV Theorem does not mean what people like WLC want it to mean.  In this part of the video, he very specifically says that the BGV Theorem does not conclude that the universe must have a beginning, it concludes only that expansion must have a beginning.

WLC will need to find a new argument for an absolute cosmic beginning.  Well, he should, but given his track record, it’s likely that he will just ignore inconvenient statements by the people whose arguments he misrepresents.

Luke Barnes Decloaks a Bit More

In Luke Barnes (Partially) Decloaks, I discussed how Barnes has provided hints that he is a theist.   What he hadn’t previously done is provide anything conclusive on whether he is an apologist, or intentionally giving succour to apologists.  But in a recent, very short blog post, he has now done so.

When I say "very short", I mean really, really short.  Here it is (my emphasis):

A very interesting essay from Alex Vilenkin on whether the universe has a beginning and what this implies. If you want my opinion, "nothing" does not equal “physical system with zero energy”.

This was followed by a list of related articles written by Barnes (again, my emphasis)

Of Nothing

More Sweet Nothings

A universe from nothing? What you should know before you hear the Krauss-Craig debate

Did the Universe Have a Beginning? – Carroll vs Craig Review (Part 1)

When you search Vilenkin’s essay, you will find that he mentioned the word "nothing" eleven times, once in the section "Eternal Inflation" and ten times in the section "God's proof" (two are in footnote 18 which relates to this section).

So, of all that Vilenkin had to write, Barnes only objected to the section that contains an explicit defeater to William Lane Craig's cosmological argument from first cause:

Modern physics can describe the emergence of the universe as a physical process that does not require a cause.

Noting that this section leads inexorably to Vilenkin's conclusion in "An Unaddressable Mystery":

When physicists or theologians ask me about the BGV theorem, I am happy to oblige.  But my own view is that the theorem does not tell us anything about the existence of God.

And the objection that he raises?  Almost precisely the objection raised by William Lane Craig when discussing Lawrence Krauss' A Universe from Nothing: Why There Is Something Rather Than Nothing:

Now that is absolutely fundamental to this claim by Lawrence Krauss. He ignores the philosophical distinctions between something and nothing, and says science is going to define these terms; it's going to tell us what nothing is. And what he winds up doing is not using the word nothing as a term of universal negation to mean not anything, he just uses the word nothing as a label for different physical states of affairs, like the quantum vacuum, which is empty space filled with vacuum energy, which is clearly not nothing as any philosopher would tell you. It is something. It has properties. It is a physical reality.

So what we have is a couple of physicists on one side, explaining how something can actually come from "nothing" and, on the other side, William Lane Craig and Luke Barnes quibbling about the definition of "nothing".  I'd actually add a few more physicists to the list, for instance Barnes' late nemesis Victor Stenger:

Suppose we remove all the particles and any possible non-particulate energy from some unbounded region of space. Then we have no mass, no energy, or any other physical property. This includes space and time, if you accept that these are relational properties that depend on the presence of matter to be meaningful.

While we can never produce this physical nothing in practice, we have the theoretical tools to describe a system with no particles.

…

… many simple systems are unstable, that is, have limited lifetimes as they undergo spontaneous phase transitions to more complex structures of lower energy. Since “nothing” is as simple as it gets, we would not expect it to be completely stable. In some models of the origin of the universe, the vacuum undergoes a spontaneous phase transition to something more complicated, like a universe containing matter. The transition nothing-to-something is a natural one, not requiring any external agent.

Note that the physicists have (at the very least) theoretical physics on their side, equations with data taken from observation and experiment to support their case.  William Lane Craig and his ilk, despite the support afforded to them by Barnes, have nothing more than pseudo-sophisticated wordplay and equivocation over the term "nothing" (together with hidden equivocation over the term "everything" - which in their argument means "everything with the exception of god").

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I'm pretty sure that I've made this point before, but it's worth making a few times.  In the article that Barnes addresses so briefly, Vilenkin provides a simple summary of the Borde-Guth-Vilenkin (BGV) theorem, the same theorem that William Lane Craig calls on all the time (my emphasis):

Loosely speaking, our theorem states that if the universe is, on average, expanding, then its history cannot be indefinitely continued into the past. More precisely, if the average expansion rate is positive along a given world line, or geodesic, then this geodesic must terminate after a finite amount of time.

Sure, the universe is expanding now, and there are indications that that expansion is accelerating now.  But what about on average across the whole history of the universe?  It's possible that this expansion rate has been positive throughout, but it's also possible that it hasn't or that another assumption of the BGV doesn't hold (note the comment "their model avoids singularities because of a key difference between classical geodesics and Bohmian trajectories", the BGV relies on classical geodesics).  William Lane Craig never addresses these issues; he takes it as granted that the universe has always been expanding and, to extend him some credit, the Ali-Das model was only published relatively recently (but, retracting the credit, I don't actually expect Craig to ever acknowledge the difficulties that this model presents to his argument).