The Probability Problem

I'm almost halfway through Richard Dawkins' wonderful book, The God Delusion, and am loving every page of it. Obviously the author's (atheistic) point-of-view isn't going to be to everyone's tastes, and that's fine. But he certainly makes many compelling arguments in his quest to bring rational thought to a topic that so often falls back on the "and then a miracle occurs" brand of reasoning that's anathema to most lovers of science.

However, the editor in me couldn't help but notice a place where Dawkins could have added an example to more clearly make his point. In Chapter 4, "Why There Almost Certainly Is No God", he tackles (among other things) the "so-called anthropic principle." This, as he describes it, revolves around the improbability of Earth containing exactly the right elements and environmental conditions to support life. It has to orbit within the "not too hot, not too cold" Goldilocks zone of the sun, have the right amount of hydrogen in its atmosphere, have abundant amounts of water, and so on. Each of those prerequisites has long odds against it to begin with, in terms of likelihood to occur randomly, and when you multiply them together, our situation here seems so improbable that many people point to an interventionist God as the only "viable" solution. (As Dawkins mentions repeatedly throughout the book, though, falling back on "God" to "solve" every mystery simply deepens the mystery, since something else had to create that being or cause it to come into existence, resulting in a "vicious regress".)

At any rate, Dawkins addresses this puzzle by arguing that "We exist here on Earth. Therefore Earth must be the kind of planet that is capable of generating and supporting us, however unusual, even unique, that kind of planet might be." He then goes on to show that, with at least a billion billion (i.e. 1,000,000,000,000,000,000) planets in the universe to choose from, even a one-in-one-billion chance of those kinds of conditions forming means that there are likely a billion other planets equally as capable of supporting life as Earth has proven to be. It's a good approach that I'm sure will resonate with some people.

What was missing, I thought, was an explanation of how probability works when you take perspective into consideration. Had I been providing Dawkins with feedback on a draft of this book, I would have suggested he include the following example (or something like it):

"Suppose that a wealthy billionaire dies, and his will dictates that one billion dollars from his estate be granted to one person on Earth, chosen randomly from its population. He instructs his executor to accept applications through each nation's government, and one billion names get submitted. Then one person from the list is picked through the use of randomizing software, and that individual is given a billion dollars. Each of the applicants realized that he or she had almost-vanishingly low odds at being selected. In other words, if you were one of those people, the chance of you being picked was so low as to appear to be zero unless you looked well past the decimal point. However, one person was chosen, and she wins the biggest lottery of all time. To that woman, it seems like a miracle that she was granted this incredible windfall. The odds against it happening, from her point-of-view, were so ridiculously high that it would seem almost impossible.

Life on Earth is like that scenario: it's a very unlikely event, but not an impossible one. It happens very rarely compared to the number of times it doesn't happen. Earth just happened to be one of the "winners", and that's the only reason we're here, now, wondering about the origin of life on this planet. If it hadn't happened to Earth, we wouldn't be here, just like there's no one on countless other - dead - planets to ask the question there."

I find that people often don't really get that aspect of low probability scenarios. When I'm thinking about that sort of situation, I often fall back on the lottery idea to gain the right perspective.