I've been persuaded to blog my ideas on evolution. The first point to make is that it isn't one concept: it's at least 7. I'll rate them on an A..F scale (where most of Physics would get an A+):
1. Theoretical Evolution is a mathematical theory of population-based optimisation. Subject to certain conditions (which might perhaps be formalised a little better), it works, and has been proven in practice, and used to design e.g. electrical devices. I rate the evidence for this as A+.
2. Evolutionary Adaptation is evolutionary variation within a species in response to environmental changes. This is regularly observed, e.g. with antibiotic resistance in bacteria. I therefore rate the evidence for this as A.
3. Speciation is the accumulation of adaptations until two sub-populations can no longer inter-breed and form different species. There are many traces of this occurring, and speciation of fruit flies has been demonstrated in the lab. I therefore rate the evidence for this as A.
4. Classical Evolution extends speciation to larger categories (genera, familes, orders, classes). There is highly suggestive fossil and DNA evidence for evolution (or something which in some ways would resemble evolution), but it's far too slow a process to demonstrate in the lab. In that it's a theory about the past it's inherently difficult to prove. I therefore rate the evidence for this as C to D, depending on the category.
5. Phylogenesis is the formation of the largest categories of creatures, the phyla. This is by analogy with classical evolution, but there are many more problems. First, it all seems to have happened in the Cambrian Explosion and then stopped for some unexplained reason (there have been no new phyla since then). Second, there is no fossil evidence of the process occurring (the phyla appear in the fossil record pretty much all at once). I therefore rate the evidence for this as E.
6. Abiogenesis is the origin of life from non-living matter. There is currently no properly developed theory as to how this might have occurred, just some hints. Many scientists have suggested some kind of self-replicating molecule as the start of the process, but have not been able to name a specific candidate. Properly developed ideas in this space should be testable in the lab, but this has yet to happen. I therefore rate the evidence for this as F.
7. Philosophical Evolutionism is the belief (expounded by Richard Dawkins and others) that the presence and variety of life on this planet can be explained solely by processes 1 to 6. In particular, God is not required, and this is viewed as evidence against the existence of God. Now, clearly the problems with at least phylogenesis and abiogenesis indicate that the presence and variety of life on this planet can not (at present) be explained solely by processes 1 to 6. Furthermore, the inference to the nonexistence of God is obviously invalid. I therefore rate the evidence for this as F–.