Fine Tuning and Probability

An interesting issue which illustrates the perils of probability theory – and, strange to say, Keynesian radical uncertainty – is the so-called fine tuning argument from design.

Essentially, this is the view that the universe’s physical and chemical laws appear to be fine tuned, in the sense that if only slight changes occurred in one of the various constants, the universe could not support life. Since it is deemed extremely improbable that the universe would be so finely tuned for life, this is (supposedly) evidence of a designed universe created by some kind of intelligent designer.

It is no surprise that various theists and theistically-inclined philosophers and scientists are partial to this argument.

There are many problems with it. First, there is the counterargument that the universe does not appear to be optimally fined tuned for organic life at all, but perhaps only minimally fined tuned. After all, the vast majority of the universe consists of the mind-bogglingly vast vacuum of intergalactic and interstellar space: this is filled with electromagnetic and particle radiation that is lethal to carbon-based life (except perhaps for the most robust microorganisms).

Secondly, it is far from clear that the emergence of self-replicating molecules and the subsequent evolution of complex carbon-based life is either easy or particularly common in our universe.

Thirdly, even if we could grant that there might be some convincing inductive argument in support of an intelligent designer, why would that designer have to be supernatural? Why not a being or beings who were non-supernatural and who merely arose by Darwinian evolution in another universe? (for example, perhaps such beings may have designed our universe to create stars and black holes, and life was a highly improbable accident, and so on).

But, even if all these concerns are put aside, the overwhelming problem with the fine tuning argument from design is, quite simply, the probability issue. How can anyone ever prove that the current universe with its physical laws is in fact extremely improbable in an objective sense?

This can be stated as follows:

(1) In order to calculate an a priori probability one would need a list of the complete set of possible universes (in a sample space) that might arise from the antecedent conditions before the Big Bang to the point when laws are formed. And not just that, but we must know that all outcomes are equiprobable as well. However, there is not a shred of evidence that anyone can provide either of these things: it is clear that you cannot construct a priori probabilities.

(2) what about relative frequencies? It is utterly impossible to conduct empirical tests of relative frequencies of outcomes in trials because that would require experiments in which we create the universe over and over again to see the types of universes created, and then to obtain a set of such outcomes and ascertain whether stable long run relative frequencies for outcomes occur. Hence no objective relative frequency probability can be constructed for the present universe either.

In short, the very idea that the present universe’s laws are highly improbable is unproven speculation. For all we know, our present universe might be highly probable; or might have a probability of 1; or only be moderately improbable, and so on. At the moment, however, we cannot really say.

The same thing can be said of the question:

“Why is there something instead of nothing?”

This very question presupposes that it is highly probable there should be nothing instead of something. But we have not proven that assumption at all. Perhaps, after all, it is extremely probable that there should be something like the universe instead of nothing (for example, once we get into the strange world of quantum mechanics, with its virtual particles and quantum fluctuations, strange things appear to happen).

Of course, many philosophers and skeptics are well aware of what I have said above, and many years ago the analytic philosopher C. D. Broad made the same point in a critique of the philosophical theologian F. R. Tennant:

“The Design Argument really makes two uses of the notion of antecedent probability. It has to contend both that it is antecedently improbable that the world should be such as it is without being the product of the design, and that the existence of a world-designer has an appreciable antecedent probability. Now, as regards the first point, I cannot see that Dr. Tennant has answered the objection by his distinction between ‘mathematical’ and non-mathematical probability. Is there any sense of probability, mathematical or ‘alogical,’ in which a meaning can be attached to the statement that the antecedent probability of one constitution of the world as a whole is greater than or equal to or less than that of any other? I very much doubt if there is.” (Broad 1930: 479).

These days sophisticated proponents of the fine-tuning argument from design are quick to admit that their probability estimates are not objective, but merely epistemic probabilities derived from inductive reasoning.

But even an epistemic probability depends on the amount or degree of relevant knowledge (Skyrms 2000: 23), and if this isn’t an example of an issue where we face something close to radical uncertainty (in the Keynesian sense) – where the weight of evidence must be very small (perhaps close to 0) – then I don’t know what is.

BIBLIOGRAPHY
Broad, C. D. 1930. “Philosophical Theology, Vol. II.: The World, the Soul, and God, by F. R. Tennant,” (Review) Mind n.s. 39.156: 476–484.

Shotwell, David A. 1987. “Is the Universe Improbable?,” Skeptical Inquirer 11: 376–382.

Skyrms, B. 2000. Choice and Chance (4th edn.). Wadsworth, Belmont, CA.