09 February 2013

Causality and fine-tuning the universe (Or, Craig/Vilenkin part 4)

Broadly speaking, Many Worlds in One can be divided into four conceptual sub-sections:
  • The development, successes and difficulties of inflationary cosmology
  • The speculative implications of the mathematics used to develop inflationary theory, including the existence of a multiverse
  • The beginning and end of the universe
  • Quantum models that show a "universe from nothing"
Unsurprisingly, William Lane Craig (in his review of the book here) is eager to jump on board with Vilenkin regarding the beginning of the universe. However, as has been discussed in the first part of this series, Craig is equivocating. While Craig's Kalam Cosmological Argument argues that the universe was instantaneously materialized out of complete and absolute nothingness, Vilenkin only says that cosmic inflation cannot be past-eternal, and we must use other physics (i.e., quantum models instead of classical models) to describe the boundary condition. To paraphrase Stephen Hawking, classical Big Bang models (including inflationary cosmology) cannot be used to predict how the universe began – only how it evolved afterward.

This is not a point to be overlooked when addressing the Kalam. In order for a deductive argument to be sound, its premises must be unequivocally true. Quantum cosmology models such as Vilenkin's postulate a universe that can come into being without an external cause. While they are indeed speculative, they are also based on well-established mathematical models. Craig essentially has two options. The first is that he can reject the very notion, prima facie, that quantum models in principle can be valid descriptions of the universe. That would a precarious position given the astounding progress physicists have made in just the last century alone. His other option, and the position he takes in his review, is to equivocate:

[If] Vilenkin's theory of quantum tunneling provides an account of how the universe can arise without a material cause, then the theist may freely avail himself of it also. The advantage of theism over naturalistic accounts is that theism provides an efficient cause of the universe, whereas naturalism cannot.
Notice that in the Kalam itself, Craig doesn't specify what he means by "cause". He never mentions "efficient" or "material" causation. What he does make clear, though, is that the universe needs some type of cause to bring it into existence. This is directly in conflict with Vilenkin's quantum tunneling model, which unambiguously states that it allows the universe to begin to exist without a cause. Here, Craig is saying that the theist can still insert an "efficient" cause without rejecting Vilenkin's ideas prima facie, but he carelessly neglects the fact that doing so is utterly superfluous, meaningless, and scientifically useless.

Fine-tuning the universe

Also unsurprisingly, Craig is considerably less receptive to Vilenkin's ideas about the multiverse and quantum tunneling – which Craig argues are attempts to "explain away" God's hand in creating the universe. Note the language Craig uses in describing Vilenkin's concepts (emphasis mine):
Postulating many worlds enables one to avoid the inference to design, which might be taken to place homo sapiens (the most complex structure in the world) at the center of the universe. The delight in duplicate worlds springs from the consequent dethronement of mankind as the crown of creation.
But if an infinite ensemble of simultaneous island universes does not actually exist, Vilenkin's attempt to explain away the fine-tuning of the universe for intelligent life collapses.
Craig is clearly trying to paint Vilenkin as someone who doesn't like the idea of God creating the universe, and the supposed "fine-tuning" of the universe is something that he has to "explain away". But this is extraordinarily disingenuous. Vilkenkin is actually talking about one of the biggest problems in physics: the cosmological constant. Namely, why do we observe the precise value we do? Why is it so different than the predicted value (see the cosmological constant problem)?

It's important to understand what, exactly, Many Worlds in One really is. Vilenkin first describes the development of inflationary cosmology, and how it has made many astounding and successful predictions. However, the mathematics underlying the structure of inflationary theory are not well-understood (i.e., the initial conditions that lead to inflation). Vilenkin discusses various mathematical models that attempt to describe those initial conditions, and then fully explores the implications of these mathematics -- which leads into multiverse verse theory, among other bizarre possibilities.

There are three things to be said about Craig's position. The first is that expressing incredulity at speculative physics because they seem counter-intuitive or violate one's favored philosophical positions is a vacuous and naive reaction. Many discoveries in physics have proved to be remarkably counter-intuitive and may have unsettling implications, but they are true nonetheless.

The second is that if Vilenkin were to reject all these mathematics and simply accept Craig's version -- that the universe is the way we observe it because God made it that way -- nothing will actually have been explained. Since life-supporting universes could arise with different cosmological constants, why is the cosmological constant just as we observe it and not a different value? Multiverses arise from inflationary mathematics, and these other universes -- if they exist -- may indeed have different cosmological constants. Why is that the case? Why should we find ourselves in this universe, and not a similar one? Why is the universe expanding at all? Why is this expansion accelerating? These are all questions Vilenkin tackles. Craig's answer? Because God, that's why. It's truly no answer at all.

The third is that Craig's language above betrays an uncritical bias: "the fine-tuning of the universe for life". Given the extraordinary rarity of life even in the most generous of speculative circumstances, we might as well say the universe was fine-tuned for vast empty voids, black holes or inhospitable gas giants. It's far more parsimonious to state that life is fine-tuned -- i.e.,  adapted -- to a rare but possible set of circumstances in the universe, not vice versa.

In the last entry, I'll talk about the beginning of the universe according to Vilenkin -- the "universe from nothing".

Previous entries:
Part 1 
Part 2
Part 3

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