Saturday, January 14, 2012

Free will and fine tuning

There is good reason to think that we do not have free will and that the fundamental constants of physics are not fine tuned. Some people defend theism on the grounds that both phenomena are evidence that naturalism is insufficient to describe or explain the universe. So the evidence that both are false assumptions has some significance in the debate over whether or not we should believe that there are no gods.

I will utilize biologist Jerry Coyne's definition of free will: When faced with two or more alternatives, it's your ability to freely and consciously choose one, either on the spot or after some deliberation. A practical test of free will would be this: If you were put in the same position twice — if the tape of your life could be rewound to the exact moment when you made a decision, with every circumstance leading up to that moment the same and all the molecules in the universe aligned in the same way — you could have chosen differently.

If we had free will then we would be self-aware of the action we have selected before we have irreversibly committed to that action. If our choices are unconscious, having been determined well before the moment we think we've made them, then we don't have free will in any meaningful sense. Scans of brain activity favor the latter scenario. First we irreversibly commit to an action and we become aware of which action we are taking only after the decision was made. For example, brain scans show that when a subject "decides" to push a button on the left or right side of a computer, the choice can be predicted by brain activity before the subject is consciously aware of having made it. We then convince ourselves post-hoc that we decided on our action after conscious deliberation. Thus, our feeling that we consciously choose may be a deeply ingrained and automatic self-deception, a trick our mind plays on us.

In his new book "Who's in Charge: Free Will and the Science of the Brain", neuroscientist Michael Gazzaniga explains how the right brain hemisphere is driven by the senses and acts on an immediate, subconscious level. The left brain hemisphere applies a conscious after-the-fact reasoning that attempts to make sense of the actions that the subconscious mind has already taken. The left-brain's "interpreter module" is always at work inventing theories to "explain" what the right half of the brain has already "decided" on the basis of reflexive subconscious instinct.

Our intuition that we have free will is very strong. The concept of free will is fundamental to the way people assign meaning to their lives and is perceived as continuously being in play except when we are sleeping. But from a biological perspective, conscious self-awareness of actions came later in the history of life. Life originally selected among alternative available actions without self-awareness. So it makes sense that animals which later acquired conscious self-awareness still tend to make decisions prior to being self-aware of those decisions.

The premise of the fine-tuned universe assertion is that a small change in several of the dimensionless fundamental physical constants would result in a universe that cannot support life. The current standard model of particle physics has 25 freely adjustable parameters. However, the standard model is not mathematically self-consistent under certain conditions, so most physicists believe that it is incomplete. In some candidate replacement theories, the actual number of independent physical constants may be as small as 1. But, for the sake of argument, let's accept that there are 25 and that a small change to any single one of these constants makes the universe radically different.

Fine tuning can be cited as evidence for an intelligently designed universe only if the probability that the universe would be able to support life is tiny over the entire spectrum of all possible combinations of all possible values of all the constants. Even if the fine-tuning premise were true, there is theoretical evidence for a multiverse which provides a naturalistic explanation for fine-tuning. But is the premise true? Varying the value of just one constant while leaving all of the other values at their actual values may result in no other universe that can support life. Yet varying the values of all 25 constants simultaneously may result in many universes that can support life. The former result can thus be misleading, because the latter result, if true, would outnumber, and thus defeat, the former result.

Simulating universes while simultaneously varying the values of all 25 constants may be computationally very difficult, but several attempts have been made with a subset. Victor Stenger has simulated different universes in which four fundamental parameters are varied. He found that long-lived stars could exist over a wide parameter range. Fred Adams has done a similar study to Stenger, investigating the structure of stars in universes with different values of the gravitational constant, the fine-structure constant, and a nuclear reaction rate parameter. His study suggests that roughly 25% of this parameter space allows stars to exist.

So the free-will and fine tuning arguments may both be wrong. Certainly, both arguments have been premature in the sense that neither phenomena has been established to be true by the evidence. It is only very recently that we have acquired the tools to start to tackle the question of whether these two premises are true. The early results suggest both premises are false.

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