Post Author: Bill Pratt

In part 1 of this series, we learned that there are two versions of the multiverse hypothesis, level 1 and level 2.  The level 1 multiverse is non-controversial as it is basically an extension of our current universe in space.  The level 2 multiverse, however, makes much grander claims and is fraught with problems.  We pick up with cosmologist George F. R. Ellis’s Scientific American article from August 2011.

So what is wrong with the level 2 multiverse hypothesis? Ellis explains:

What is new is the assertion that the multiverse is a scientific theory, with all that implies about being mathematically rigorous and experimentally testable. I am skeptical about this claim. I do not believe the existence of those other universes has been proved—or ever could be. Proponents of the multiverse, as well as greatly enlarging our conception of physical reality, are implicitly redefining what is meant by “science.”

Why is the level 2 multiverse not scientific?

The key step in justifying a multiverse is extrapolation from the known to the unknown, from the testable to the untestable. You get different answers depending on what you choose to extrapolate.  Because theories involving a multiverse can explain almost anything whatsoever, any observation can be accommodated by some multiverse variant. The various “proofs,” in effect, propose that we should accept a theoretical explanation instead of insisting on observational testing. But such testing has, up until now, been the central requirement of the scientific endeavor, and we abandon it at our peril. If we weaken the requirement of solid data, we weaken the core reason for the success of science over the past centuries.

Ellis sympathizes with those scientists who posit the level 2 multiverse as a “way of resolving deep issues about the nature of existence,” but he argues they are misguided. 

All the same issues that arise in relation to the universe arise again in relation to the multiverse.  If the multiverse exists, did it come into existence through necessity, chance or purpose?  That is a metaphysical question that no physical theory can answer for either the universe or the multiverse.

The level 2 multiverse, then, is not a scientific explanation, but is philosophical speculation.  It is an alternative metaphysical idea that is simply meant to replace the metaphysical idea of a supernatural Designer.  Those skeptics who constantly chastise Christians for doing metaphysics, and who then turn around and posit the level 2 multiverse as the cause of the fine tuning of the universe, find themselves also doing metaphysics. 

It seems that skeptics come to a fork in the road here.  Either admit that metaphysics is unavoidable and climb onboard with theists, or stop offering the multiverse as an explanation to anything.  What skeptics may not do is claim that they are only offering scientific explanations while at the same time arguing for the multiverse.  That door is closed.