Some people object to The Fine Tuning argument because they say that just because it’s extremely improbable does not warrant the conclusion that the universes various constants and quantities were designed to take those values. If you haven’t heard of The Fine Tuning Argument before and have no idea what I’m talking about, go read the article “The Fine Tuning Argument For God’s Existence (Updated Version)”.
After all, improbable things do happen. It’s extremely improbable, for example, that your mother and your father should just happen to meet when and where they did, and that your grandparents just happen to meet when and where they did so that your parents would be born. But we wouldn’t say that that therefore it was planned for your parents to meet as they did. We might believe their meeting was planned, perhaps on the basis of divine providence if one is a Christian theist, but the conclusion that your parents meeting was destined would be on theological grounds, not its high improbability of occurring. The high improbability alone would not justify the conclusion that it was set up by intelligent design.
So then, why do we rule out chance when it comes to the fine tuning argument? Well, here is where the question of how we recognize design arises. The dean of the contemporary Intelligent Design movement William Dembski argues that in addition to high improbability there also needs to be conformity to an independently given pattern. When these two elements are present, we have what Dembski calls “specified complexity,” which is what leads us to conclude that what we’re seeing is the result of an intelligent designer.
It’s like this; imagine you walk into a clock store and you see all of the clocks set at random times. One of them is set at 2:00, another one is set at 3:14, another one is set at 7:45, another one is set at 9:23, and so on. Now, it is highly improbable that each and every clock should be set and the times that they are set at. It is extremely improbable that the first one should set at 2:00, the one next to it be set at 3:14, the one next to that be set at 7:45, and the one next to that be set at 9:23. What are the odds that just that combination of time settings should line up in exactly that way? Why wasn’t the first clock, instead of being set at 2:00 be set at 1:15? Or why wasn’t the one next to it set at 3:00 instead of 3:14? Should you conclude design? Or rather, would you conclude that someone had set those clocks at exactly the time that they were set? Probably not. Why? Because even though it’s improbable that all of the clocks would just so happen to be set in that way, any combination is equally as improbable as any other.
However, now let’s suppose that instead of seeing each clock set at 2:00, 3:14, 7:45, and 9:23 respectively, you instead see that each clock is set at just the right time, that is to say, the time of day that it actually is. At every clock you look at, you see that each and every clock is set at the correct time. Not a single clock has the wrong time on it. Now, would you conclude that this particular setting of clock times was the result of intelligent design? Of course! Why? After all, isn’t this combination of clock settings equally as improbable as any other? Isn’t this clock setting as improbable as the combination above? Of course. However, it’s not just the high improbability of the clocks being set that way that tips you off to design. Rather, it is the extreme improbability plus the fact that the row of clocks conform to a specific pattern. High improbability plus conformity to an independently given pattern.
In the same way, we don’t rule out the chance hypothesis in the fine tuning argument merely because of how improbable it is that each and every constant and quantity should take the values that they do. But also because the finely tuned constants and quantities all follow a specific pattern. What is that pattern? The pattern is that each and every physical parameter has to fall within an extremely narrow life permitting range. 99.99% of the possible values each constant and quantity could take is a value that, if taken when the universe sprang into being, would render the universe life prohibiting rather than life permitting. 99.99% of the different values that these physical constants and quantities could take would have rendered the universe life prohibiting. Only 00.01% of the possible ranges would allow the universe to harbor life. And it is the fact that each constant and quantity falls into that life permitting range, rather than the innumerable life prohibiting ranges, which give the fine tuning of the universe that independently given pattern that makes chance so implausible.
For example, it is the fact, that only 1 part out of 10^100 different settings the Weak Nuclear Force could have fallen into is life permitting, and that that is the value that the weak nuclear force took, that causes to us to believe that it was intelligently designed to be in that 1 part. And the same goes for all of the other parameters.
Just as each clock in my above illustration was tuned to reflect the correct time of day, so the laws of physics are each tuned to the setting required for life of any kind to exist anywhere in the universe. However, if you read the article I linked to both above and below (called "The Fine Tuning Argument (Updated Version)", you’ll notice that the odds of the universe being fine tuning for life is orders of magnitude more improbable that a shop full of clocks reflecting the correct time by sheer chance.