Are the multiverse theories scientific?

Virgo galactic cumulus

In previous posts I have said that the theories of the multiverse (there are several, some of them contradictory to the others) are not scientific, because it’s not possible to prove them false, according to Karl Popper’s criterion: a theory is not scientific unless it can be proved false with an experiment.

A recent article by Man Ho Chan reviews and refutes various attempts to claim that multiverse theories are indeed scientific. Here I am going to speak about those that try to prove that the multiverse theories should be considered scientific without asking big changes to the current criteria. Carroll 2018 uses three main arguments to justify this:

Karl Popper

1. By asserting that the multiverse theories meet the conditions of falsifiability. According to Sean Carroll, falsifiability is not a true/false criterion, but rather admits nuances and degrees of compliance, between the total impossibility and the total possibility of proving that a theory is false. Between these two extremes, there would be at least three intermediate degrees: a) it is possible to prove it false with a thought experiment theoretically impossible to carry out; b) it is possible to prove it false with a thought experiment impossible to carry out in practice; c) it is possible to prove it false with a thought experiment that can be performed, but would only provide a partial demonstration. According to Carroll, a theory that satisfies a), b) or c) should be considered scientific. Man Ho Chan points out that multiverse theories do not meet any of these three conditions and, therefore, according to Carroll’s premises, cannot be considered scientific. A curious point: Carroll proposes in his article a few examples of theories that are not scientific, according to his own looser criteria, and among them he mentions Marxism and the theories of Freud and Adler.
2. In the same article, Carroll offers another criterion, according to which multiverse theories could be scientific, which consists in applying the inference to the best explanation, also called the no-miracle argument, which I discussed in another post. His reasoning is this: Multiverse theories are the best explanation for the fine-tuning problem. We have no better explanation. Therefore, we must consider them scientific. Man Ho Chan points out that we do have another explanation, which also meets the conditions established by Carroll: the creation and design of the universe by God. However, apart from proponents of Intelligent Design, no one has proposed that this theory be considered scientific. Therefore, multiverses should not be considered scientific either.
3. Finally, Carroll resorts to another argument. We must consider the theories of the multiverse scientific because we have no other alternative to explain the mystery of the cosmological constant, which I discussed in another post. According to Carroll, for a theory to be scientific it should be enough a) that it can be true and b) that it influences how we understand what we observe. Man Ho Chan points out that the existence of a Creator also explains the value of the cosmological constant, and meets the two conditions set by Carroll, although this theory is not considered scientific; therefore, the multiverse theories should not be considered scientific either, and the criterion proposed by Carroll is not sufficient.

In the next post I will talk about epistemological changes: attempts to make scientific theories of multiverse theories by modifying the currently dominant scientific paradigm.

The same post in Spanish

Thematic Thread on Multiverse and Fine Tuning: Previous Next

Manuel Alfonseca