Fine tuning arguments are one of the more recent, popular versions of the argument from design. The goal, like all arguments for the existence of God, is to produce an argument that would make it reasonable to believe in God starting from premises that do not assume the conclusion. In the case of the fine tuning argument, the delicate balance of finely tuned physical laws, constants, and variables that are held up as evidence that some powerful, knowing, and caring being with a plan must be responsible for the universe we live in.
In one form or another, these arguments build on the premise that were it not for some intervention, or some unnatural force, matter would not align itself according to just those physical laws that are conducive to the survival and flourishing of life rather than some others. There are infinitely many different values and forms that physical laws could have taken. Gravity could have been stronger, light could have been slower, the cosmological constant could have been larger, or there could have been no gravity and no light at all. But the laws that obtain are obviously amenable to the existence of life. Our world has stable, complex elements such as carbon, and rich, long burning energy sources such as stars to fuel the growth and development of life. If any of the physical values, such as the cosmological constant, had been varied even slightly, none of those biophilic results would have obtained.
And science itself cannot resolve the question, we are told, because science is confined to describing the order, not determining why there is order at all.
So given the choice between an infinite list of possible physical worlds where only a narrow range of them are hospitable to life, and a universe that contains a divine being who deliberately devised physics to favor life, the reasonable person must believe in God, concludes the fine tuning argument.
But there’s a grave mistake lurking here. And the mistake is exposed with a few questions. Suppose we are considering supernatural beings who could be responsible for devising the world the way it is and they have some reasons that we are not privy to. How many different beings of this sort could there be?
Before we answer, consider a few other questions: Is it necessary to possess omnipotence in order to create a universe? It would seem so, but what if that was all that the being could do, or it could build one, but only one that is inferior in several ways. For all we know, it could have been this being. How much knowledge is required in order to create a universe? Not omniscience. It is often possible to create something greater than you are, or to create something accidentally. Or it is possible to create something that you thought would have one set of features but it turned out completely different. And clearly, infinite goodness wouldn’t be required to create a universe. A being could have only a finite amount of good will. Or it would even be malevolent. Maybe things in our world are about to get much, much worse than they currently are. All of the good times we’ve been having were just to lull us into a false sense of security.
So there is actually a wide range of beings, many of them less than omni-beings, who could possibly be responsible for our universe. And they could have lots of different hidden reasons for building it the way we find it.
Now back to our question: if we find ourselves in a universe and we wonder how many different kinds of beings, of different levels of goodness and ability, might have been responsible for causing it, how long would our list be? How many possible gods are compatible with the universe we find ourselves in? An infinite number. For a list of 500, see 500 Dead Gods
Now we can see the fatal flaw. A godless universe was rejected in the fine tuning argument because of all the possible configurations that matter could behave according to, only a few are conducive to life. The odds, we have been told, are astronomically small that physics would just happen to end up the way it ended up.
As long as we only consider a single God hypothesis, then it would seem that the designer argument gives us substantial support in its favor. But if there is an infinite number of possible gods who might have made this universe for reasons that are unknown to us, and we settle on believing that a particular one—the Christian God, for instance—must be THE one that did it to the exclusion of all the others, what are the odds that we settled on the right God? Aren’t the odds that it was this God rather than one of the infinitely many others astronomically small? Then how is it by the fine tuning argument that the God hypothesis is preferable to an atheistic hypothesis? We’re left with a stalemate. As long as we’re giving due consideration to all of the possibilities, we won’t be able to choose from among all the options without revealing some presumption or prejudice. So the fine tuning argument leaves us back at square one for deciding on the origins of the universe.
If we can’t decide between all of these infinitely many possibilities a priori, then what method or approach could give us any means of discrimination that would be rational to adopt? We would need a method that would allow us to investigate various possibilities, make predictions, test them, and then reject the ones that don’t fit with the data. We need the scientific method, not religious dogma, to allow us to investigate the foundations of the universe. Religious dogma cannot give us any reasons to prefer one hypothetical God over another, aside from its bold, confident assertions that it is correct.
Some similar concerns lead Steven Weinberg to say about fine tuning arguments,
“But religious theories of design have the same problem. Either you mean something definite by a God, a designer, or you don't. If you don't, then what are we talking about? If you do mean something definite by 'God' or 'design,' if for instance you believe in a God who is jealous, or loving, or intelligent, or whimsical, then you still must confront the question 'why?' A religion may assert that the universe is governed by that sort of God, rather than some other sort of God, and it may offer evidence for this belief, but it cannot explain why this should be so.” A Designer Universe: http://www.physlink.com/Education/essay_weinberg.cfm
The only way they can get the argument to appear to work initially is by holding an infinite number of alternative possibilities against the hospitable universe we find ourselves in while artificially narrowing the field of supernatural explanations to one. But since there are just as many alternative god hypotheses that would fit the data that they wish to emphasize, there can be no grounds for preferring the traditional omni-God or Christian God hypothesis over the others except by building it in as the only choice from the start. Only through this circularity and unanalyzed initial assumptions does the Fine Tuning Argument have even a glimmer of plausibility. And now we can see that it doesn’t even really have that.