Sunday, 5 October 2014

Objections against the Fine-Tuning Argument-II

Objection: The fine-tuning argument states that a universe with just-right conditions for life is extremely, extremely improbable- almost like balancing a planet on a razor's edge. But we could only make probability judgments based on more than one event. We can only say that a fair coin has equal probability of landing on either side because we have observed countless coin flips. Surely we cannot make that judgment when it comes to the universe, simply because there is only one of it. As Hume argued, we can only know if the universe was improbable or not if we had multiple universes to observe. Therefore, it makes no sense to ask questions like "How (im)probable is it that the cosmological constant would have the exact value that it does?"

Response: The objector is equivocating between "statistical probability" and "probability in general". Statistical probability is the type the objector has in mind- when we make probability judgments based on induction and the past data available to us. However, and this is a crucial point- this is not the only sort of probability. Clearly, in modern scientific practice we have many events that are non-repeatable. Cosmology and evolutionary biology are filled with events that happened in the past only once. Does that mean we cannot draw scientific conclusions about, say, what happened immediately after the big bang, or how the dinosaurs went extinct? The entire enterprise of historical science deals with such one-time events.

Even without appealing to scientific practice, one can intuitively know that the objection is wrong. Consider this example (borrowed from John Leslie's book Universes)- you are given a large urn filled with a million balls, and you are told that the balls are either all white, or all black, or a mixture of the two of an undefined ratio. You are then asked to randomly pick one ball. If you observe the ball is black, it gives you strong reason to believe that the rest of the balls in the urns aren't all while. This is because it is very unlikely that you would "happen" to pick just that one black ball among a million white ones. Note that you can come to this conclusion even without repeating the procedure.

Finally, the objection proves too much. Even if the stars were arranged to explicitly spell out MADE BY GOD, the objector's logic would still have us say that since we have only one universe to observe, we can't really say if this is improbable or not. Or consider a more relevant example, this too borrowed from Leslie: Let's say scientists find that the ratio of the strengths of the strong and weak nuclear forces is exactly 0.0200102002010000121102020002221002200000102022000. Now it is clearly unlikely that working with the decimal system, the entire ratio would be made up only of 0's, 1's and 2's. So the scientists, suspecting the existence of a hidden message, converts the 0's, 1's and 2's into dots, dashes and spaces, upon which the ratio spells out the famous Qur'anic verse: "So which of the favors of your Lord will you deny?" (don't try this with the number I gave above, I pulled that out of thin air) Would it be at all sensible to say that we don't know how probable or improbable such a universe is? Certainly not.

To conclude: Statistical probability, which the objection hinges on, is just one type of probability, and we can clearly draw conclusions based on other conceptions of probability. We do this in scientific practice and everyday reasoning all the time. Additionally, strong reductio ad absurda can be provided against the objection, which demonstrates the reasoning of the objector is wrong.

One last question might be: What is the exact nature of this other kind of probability that I mentioned? The technical aspects of it have been discussed in some detail in the Robin Collins essay here. This short excerpt from the essay illustrates not only the need but also some basic concerns as regards the justification of epistemic (non-statistical) probability:

Now that we know what we mean by epistemic probability, it is time to consider how it is justified. In science, many times epistemic probability is determined by an appeal to intuition, such as many of the epistemic probabilities considered in the last section –for example, those arising in conjunction with the Thesis of Common Ancestry, continental drift theory, and atomic theory. These probabilities clearly were not justified by an appeal to statistical improbability – for example, we have no statistics regarding the relative
frequency of life on a planet having those features cited in favor of evolution either under the evolutionary hypothesis or under some nonevolutionary hypothesis. Indeed, these judgments of epistemic probability were never rigorously justifi ed in any way. Rather, after (we hope) doing their best job of looking at the evidence, scientists and laypersons made judgments of what kind of world we should expect under each hypothesis, and then they simply trusted these judgments. This sort of trust in our judgments of epistemic probability is a pervasive and indispensable feature of our intellectual life.

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