Anthropic principle
From RationalWiki
The anthropic principle is a teleologic argument used most often to counter arguments for intelligent design. Those who believe in ID often argue that the multiple contingencies required for us to have come into existence are tenuous and improbable, therefore there must have been a design or plan. The anthropic principle counters that since we are here, any arguments of contingencies are irrelevant--we are already here, the probability of our existence is 100%, so the universe must be adequate for our existence, otherwise we should not be having such a dull argument.
The ID argument from contingencies is also an example of begging the question. We do not know if changing any physical constants in the universe would render life impossible. The anthropic argument counters this idea, but it has its flaws. As a teleologic argument, it takes a "it just is" approach, which could be argued is a "conversation-stopper", much in the way "Goddidit" is. However, the anthropic principle is at least true, in the sense that the universe is hospitable to us, our existence being the primary proof.
[edit] Fine-tuned universe
The anthropic principle is often associated with the concept of the "fine-tuned universe" - the idea that if any one of several fundamental constants were slightly different then stars would not form and life would be impossible. This argument is sometimes used to support the idea that he universe was "designed" as it is claimed that this situation is so highly improbable that it must be deliberate.
However in August 2008 New Scientist ran an article "In the Multiverse Stars Burn Black" [1] in which it pointed out that the above assumption is simplistic. While it is true that changing one, and only one, universal constant may render life-supporting universes impossible - that is not the case if various constants are changed at the same time. When theoretical experiments were run on different potential universes with multiple variations in their constants, some 25% were found to be capable of forming stars.
[edit] Footnotes
