In arguing against Dinesh D'Souza's claims that physics suggests the existence of an afterlife, you bring up yet another thing that supports belief in God. That is the fine-tuning of the conditions of the universe to support life. You mentioned Martin Rees' book Just Six Numbers, about the way physical constants are set perfectly to make the universe hospitable. Don't you find this at all suspicious? To me this is one of the strongest proofs of God's existence -- that if any one of these constants was just a little different, we wouldn't be here.I've heard this claim before. It's called the Strong Anthropic Principle -- that the "fine-tuning" of the physical constants of the universe implies a Fine Tuner. Far from finding this "suspicious," I simply respond that it's hardly surprising that we live in a universe that has hospitable conditions; without them we would never have come to be. (This is called the Weak Anthropic Principle -- that human existence is contingent on benevolent values for a variety of physical constants, not the other way around.)
Think, for example, of going outside on a warm, June day, and a friend of yours asks, "Why is the weather perfectly comfortable for humans today?" There are a variety of possible answers:
1) Because god wants to be happy, so he made today's weather nice.
2) Because a divine being fine-tuned the conditions on Earth to mostly create weather which humans will find congenial.
3) Because if the conditions on Earth were outside of a reasonable range of temperatures and chemical compositions, life could never have arisen here.
These three answers correspond to the three most common responses to the same question writ large (Why does the universe have conditions that support life?): (1) god as micromanager; (2) the Strong Anthropic Principle; and (3) the Weak Anthropic Principle. I find it interesting that no one seems to find it very odd that the Earth has (mostly) human-friendly climates, and most people see no need to ascribe that to god's direct intervention -- while Christians with a scientific bent go gaga when they find out that if (for example) the amount of energy released by hydrogen fusion was 5% less, stars would not exist, and therefore neither would we. The fact that there are many such initial conditions (Rees identifies six, but there are probably others) is seen as admitting only one possibility; god made the universe with us in mind.
Well, I'm not convinced. There is no underlying reason that physicists have found for why the fine structure constant is equal to 1/137 -- yet. The big deal Rees makes over the "six numbers" in the title is that they can't be derived from first principles; they seem arbitrary, empirically measured, to have no particular reason that they are what they are. I wonder very much, however, if this is necessarily true. It is entirely possible that all of the universal constants will turn out to be derivable, and therefore consistent with an overarching theory that simply hasn't been discovered yet.
However, my arguing from the standpoint of a Grand Unified Theory that may not exist is weak at best, and I'm not going to put too much weight on it. To me, the only thing that is proven by the values of the universal constants is how dependent the universe's existence is on physical conditions I barely understand. The Weak Anthropic Principle is fine by me; just as no one wonders why the weather is pleasanter on the Earth than on the surface of the sun, it's no great wonder why we live in a universe that has conditions congenial to the formation of matter, stars, complex compounds, and life. If any one of those conditions didn't exist, we wouldn't be here to ask the question.
In any case, I highly recommend Rees' book. It's well-written, and if not exactly an easy read, is at least approachable by the layperson. And even if the deliberate fine-tuning of the Strong Anthropic Principle doesn't appeal to me, I am still in awe at the delicate sensitivity of matter and energy to the settings on dials we have just begun to understand.