I’ve just finished listening to a debate between philosopher William Lane Craig and cosmologist Lawrence Krauss on the debate topic “Is there evidence for God?”. I have a load of these on my iPod – some are very good (Craig vs Austin Dacey is probably the best), while some represent 2 hours of my life that I’ll never get back. They get a bit repetitive after a while. The debate with Krauss was somewhere in the middle. Craig was polished and concise, presenting the same 5 arguments (contingency, Kalam, fine-tuning, moral, resurrection of Jesus) he’s presented for decades. Krauss was less organised and much less focussed. I’ve responded to some of Craig’s claims elsewhere. I’ll focus on some of what Krauss said.
First and foremost, I’m getting really rather sick of cosmologists talking about universes being created out of nothing. Krauss repeatedly talked about universes coming out of nothing, particles coming out of nothing, different types of nothing, nothing being unstable. This is nonsense. The word nothing is often used loosely – I have nothing in my hand, there’s nothing in the fridge etc. But the proper definition of nothing is “not anything”. Nothing is not a type of something, not a kind of thing. It is the absence of anything.
Some of the best examples of the fallacy of equivocation involve treating the word nothing as if it were a type of something:
- Margarine is better than nothing.
- Nothing is better than butter.
- Thus, margarine is better than butter.
We can uncover the fallacy by simply rephrasing the premises, avoiding the word nothing:
- It is better to have margarine than to not have anything.
- There does not exist anything that is better than butter.
The conclusion (margarine is better than butter) does not follow from these premises.
Now let’s look at Krauss’ claims again. Does it make sense to say that there are different types of not anything? That not anything is not stable? This is bollocks. What Krauss is really talking about is the quantum vacuum. The quantum vacuum is a type of something. It has properties. It has energy, it fluctuates, it can cause the expansion of the universe to accelerate, it obeys the (highly non-trivial) equations of quantum field theory. We can describe it. We can calculate, predict and falsify its properties. The quantum vacuum is not nothing.
This suggests a very simple test for those who wish to talk about nothing: if what you are talking about has properties, then it is not nothing. It is pure equivocation to refer to the quantum vacuum as nothing when a philosopher starts asking the question “why is there something rather than nothing?”. She is not asking “why are there particles rather than just a quantum vacuum?”. She is asking “why does anything exist at all?”. As Stephen Hawking once asked, why does the universe go to all the bother of existing?
We can now see that this question cannot be answered by any of the methods we normally call scientific. Scientific theories are necessarily theories of something, some physical reality. Equations describe properties, and thus describe something. There cannot be equations that describe not-anything. Write down any equation you like – you will not be able to deduce from that equation that the thing that it describes must exist in the real world. Existence is not a predicate, as Kant memorably explained.
The question ”why does anything exist at all?” may have no answer, or it may be meaningless, or it may find its answer in an entity that exists necessarily rather than contingently, or perhaps because there are many more possible worlds that contain something rather than nothing we can argue that the probability of nothing existing is low (van Inwagen, see also Mawson). We can be certain that the answer is not “because empty space is filled with quantum fields that can create particles”.
Thankfully, there are cosmologists whose thinking is not as sloppy as Krauss’. Let me give a few quotes to really drive home my point:
Cosmologists sometimes claim that the universe can arise ‘from nothing’. But they should watch their language, especially when addressing philosophers. We’ve realised ever since Einstein that empty space can have a structure such that it can be warped and distorted. Even if shrunk down to a ‘point’, it is latent with particles and forces – still a far richer construct than the philosopher’s ‘nothing’. Theorists may, some day, be able to write down fundamental equations governing physical reality. But physics can never explain what ‘breathes fire’ into the equations, and actualised them into a real cosmos. The fundamental question of ‘Why is there something rather than nothing?’ remains the province of philosophers. (Martin Rees, Just Six Numbers)
The concept of a universe materializing out of nothing boggles the mind … yet the state of “nothing” cannot be identified with absolute nothingness. The tunneling is described by the laws of quantum mechanics, and thus “nothing” should be subjected to these laws. The laws must have existed, even though there was no universe. … we now know that the “vacuum” is very different from “nothing”. Vacuum, or empty space, has energy and tension, it can bend a warp, so it is unquestionably something. As Alan Guth wrote, “In this context, a proposal that the universe was created from empty space is no more fundamental than a proposal that the universe was spawned by a piece of rubber. It might be true, but one would still want to ask where the piece of rubber came from.” (Alexander Vilenkin, Many Worlds in One)
In a quantum system, the notion of a vacuum is a little different from our usual conception of such a state. It is not simply ‘nothing at a’. Rather, it is what is left when everything that can be removed from the system has been removed: it is the state of lowest energy. (John Barrow, New Theories of Everything)
Krauss made a few other claims that were questionable – unfortunately he didn’t have much time to expand on them. It sounded like at one stage, after Craig had appealed to Bayesian probability theory, Krauss said something like: “this is not how scientists do science. Craig is talking about probabilities; I am talking about evidence”. I have no idea what Krauss meant by that. He kept saying that “evidence is falsifiable”, which isn’t quite correct. It is hypotheses that are confirmed or falsified by evidence.
He also kept asserting that the universe is not fine-tuned. At one point he implied that the multiverse explained fine-tuning, in which case the universe is fine-tuned and we know how. The only specific example Krauss gave was entropy. After Craig discussed the low entropy of the universe, as calculated by Penrose, Krauss responded by describing reheating in inflationary theory (I think). When inflation ends, the decay of the inflaton reheats the universe, refilling it with radiation to replace the energy which was diluted so dramatically by inflation. This has nothing to do with what Penrose is talking about. Penrose is concerned with the entropy associated with the degrees of freedom of the gravitational field, while reheating is about the entropy associated with ordinary matter and radiation. Penrose’s point is that, while a uniform distribution of energy is a high entropy state when we only consider the degrees of freedom of ordinary matter/radiation, it is an extraordinarily low entropy state of the gravitational field i.e. the entropy of spacetime itself. Once again, Krauss ran out of time before he really explained himself, so I’m not sure if I fully understood him.
In any case, I’ve ranted for long enough. I’m continually shocked at how poorly Craig’s opponents do. His opening speech remains almost unchanged after a few decades. You can watch his debate with Frank Zindler in 1993 and get 90% of his opening speech today. Krauss made some good points, but was in general very underprepared. We’ll see if Sam Harris can do any better …