On my blog here I've written several times responding to the Cosmological Argument for god's existence and the various moral arguments, but I've only once written about the Fine Tuning Argument head on. I want to take some time expounding on some of its implications and the problems I think it has in a bit more detail than I previously did.
1. The fine tuning of the universe is either due to physical necessity, chance or design.
2. Fine tuning is not due to either physical necessity or chance.
3. Therefore, it is due to design.
The Fine Tuning Argument poses what seems to be another tough obstacle for the atheist. The probability that all the elements in the universe would be as meticulously fine tuned to unfathomable levels that would allow life as we know it, are incomprehensibly small. But as scientists tell us, events that are extremely improbable happen all the time.
1. First I always like to use the probability of me being born as an example of chance. What is the probability that I would've been born? Well first my father and mother had to meet, that took some chance. I then had to have been conceived from one particular sperm cell and egg. The chances of that are extremely rare when considering that every time a man ejaculates, as much as 100 million sperm cells are thrust outward and only one will fertilize the woman's egg - and that's if fertilization even happens at all. The chances of me being conceived just considering that one specific time when my parents tried to conceive a child, and not even considering all their other attempts, is about 1 in 100 million. When you factor in all the other attempts at conceiving a child, combined with the probability of the circumstances that lead up to their decision and attempt to conceive a child, already the mathematical odds are stupendous.
Then you have to multiply this to the chances of each of my parents being conceived and the circumstances that lead up to that event, and then do the same to their parents, and their parents, all the way back literally to the very first form of life some 4 billion years ago. The odds of this happening are unfathomable. Everyone alive today is the product of an unbroken chain of births, billions of generations in the making. The chances that any one of my distant relatives would have had a different offspring that wouldn't have been one of my ancestors, would have always been much more probable. And yet of course if this had happened, I wouldn't have ever been born, and yet I exist and I'm real. What are the chances of that?
So events that are extremely odd can happen all the time even when the odds against them are much more probable. But even this answer doesn't satisfy all the critics, so let me give a few others.