No one would be happier than I to learn that life forms could develop from other than the standard paradigm...complex carbon molecules in a water solvent. At first glance, this would violate no known physical law (ER's nonsense filter # 1) and we certainly can't rule it out. The universe does, as we have discussed before, have a penchant for unexpectedly creating highly complex structures, and we obviously have come nowhere near exploring, or even imagining, all its possibilities.

But the fact remains that we know of no other way in which highly complex self-replicating anti-entropic systems can evolve, there just is absolutely no evidence of any kind. We can't even propose reasonable alternatives to it. It is potentially possible that our machines will someday achieve the properties of life, but they are by definition artifacts of carbon-based life forms: they can exist but they could not have arisen without our intervention. Until we actually discover non-chemical, or even non-carbon, life forms, it is only prudent to restrict our speculations to the conventional regime, which certainly appears rich and widespread enough to support a variety of different organisms and biologies.

The proper role of proposals for non-organic life forms is to suggest environments and strategies where we can be looking for evidence of their traces. I have no problem with this, but until we do locate such evidence, the regime of chemical, particulary carbon, biota
already gives us a a very rich and solidly documented venue for research and speculation.