Regarding the second contribution in Meta 115, claiming that variations in the laws of physics do not make life improbable: I have found very interesting the web page I arrvied at via this discussion, namely http://www.phys.hawaii.edu/vjs/www/avoid/intel.html by Prof Stenger (Hawaii). This is by far one of the best argued purely physicalist discussions of the anthropic principle which takes that principle seriously.
But in the end in my view it does not succeed, despite the `toy universe’ provided by Prof Stenger. And to see why one can go to the web page of Max Tegmark at http://www.sns.ias.edu/~max/toe.html who shows very clearly how small the probability space is that allows life to exist. Prof Stenger’s article briefly refers to Tegmark’s work but rejects his conclusion on how improbable life is if we allow variations in the laws of physics. Why? Prof Stenger claims that non-carbon based life is just as possible as carbon based life. In my view that is just wishful thinking – it is not backed up by anything but “I think it could be so”. Many think otherwise.
The real problem is the incredible interacting structural and functional complexity of a single living cell. Any argument for another base for such levels of complexity other than the organic chemistry we know, has to somehow take that complexity seriously, rather than just making statements that it can be attained in some other way without serious supporting arguments for this claim. To be quite specific: what is the alternative mechanism that will reliably store the immense amounts of information that RNA/DNA can hold, and also allow both reliable replication and reliable reading of this information? None is in sight. Until such a mechanism is proposed, claims such as Stenger’s have no scientific backing.