The idea behind a finely tuned Universe boils down to the idea that if the fundamental physical constants in the Universe, Gravity, Electromagnetism, Strong and Weak Nuclear Force, etc., were slightly different, then chemistry and physics as we understand them would be radically different and the formation of life as we know it would be impossible. Given the fact that we know that life exists, the Universe must have been designed (finely tuned) to facilitate the formation of life.
In essence, the concept of the finely tuned Universe is the following syllogism:
1. It is exceedingly unlikely that life should exist and if physical constants were even slightly different, then life would not exist at all.
2. Life exists.
3. Therefore, since life exists, the Universe must have been designed in such a way as to facilitate life.
Theologians absolutely love the concept of the Fine Tuned Universe. I suspect the reason so many love it so fervently is not because it has any substantive logical or philosophical merit, but because for once it allows theologians to throw around really big cosmological numbers and the argument sounds good to those who don't have a strong grasp of logic. Under normal circumstances, it is atheists like me who get to talk about billions and billions of years and nonillions of chemical compounds reacting over hundreds of millions of years and sextillions of stars in the observable Universe. When theologians talk about the Finely Tuned Universe, they finally get to toss those big probabalistic numbers around like hand grenades. They get to talk about the unlikelihood of star formation if the strong nuclear force was less and use really big numbers to discuss the odds and throw out numbers like a 1 with a billion zeros.
The fact that theologians finally get to use big numbers doesn't make their arguments any better. Before discussing why exactly the finely tuned Universe is nothing but intellectual rubbish, it is instructive to consider the following logically equivalent syllogism:
1. It is exceedingly unlikely that you (referring specifically to YOU) should be reading this blog post, and if events had occurred even slightly differently then you would not be reading this blog post at all.
2. You are reading this blog post.
3. Therefore, since you ARE reading this blog post, the Universe must have been designed in such a way as to bring you to this site to read this blog post.
Obviously the Universe is NOT finely tuned to bring you to this site to read these words, but the logic is equivalent. Fact. You are reading this blog post. Fact. It is actually exceedingly unlikely that you should be reading this blog post. No one a year ago could have possibly predicted such an event – the odds would be astronomical of such an event occurring. Indeed, had any number of mindbogglingly innumerable occurrences in your daily life, or the lives of ANY of your ancestors or their evolutionary progenitors been slightly different, you might not even EXIST to be reading my blog post. And yet you ARE reading my blog post, which clearly indicates that the Universe must have been designed to ensure this result – otherwise how could such an unlikely event have occurred? Surely this result could not have been ensured without some manner of intelligent design and fine tuning of events and occurrences.
There are a number of erroneous assumptions and logical fallacies built into this conception.
First, it assumes that the Universe has a purpose.
Second, it assumes that the formation of life is the PURPOSE of the Universe.
Third, it assumes that the formation of OUR kind of life, carbon based life, is the PURPOSE of the Universe.
Fourth, the syllogism, even when reduced to its most elementary form: 1. X is unlikely because if A, B, C, D ,E, F, were different, X would not exist. 2. X exists. 3. Therefore the Universe is fine tuned to ensure X. actually works an improper substitution, introducing 'fine tuning' or 'design' or 'purpose' in the conclusion when that term does not appear anywhere in either of the propositions.
Finally, the conclusion does not logically follow from the first two propositions. It improperly seeks to affirm the consequent and does so by means of a complete non sequitor.
So the next time someone trots out the fine tuning of the Universe as a method of supporting intelligent design or the existence of God, call them out on their mildly sophisticated theological bullshit.