There are numerous definitions of naturalism. Here is one definition with some additional observations from infidels.org:
As defined by philosopher Paul Draper, naturalism is “the hypothesis that the natural world is a closed system” in the sense that “nothing that is not a part of the natural world affects it.” More simply, it is the denial of the existence of supernatural causes. In rejecting the reality of supernatural events, forces, or entities, naturalism is the antithesis of supernaturalism.
As a substantial view about the nature of reality, it is often called metaphysical naturalism, philosophical naturalism, or ontological naturalism to distinguish it from a related methodological principle. Methodological naturalism, by contrast, is the principle that science and history should presume that all causes are natural causes solely for the purpose of promoting successful investigation. The idea behind this principle is that natural causes can be investigated directly through scientific method, whereas supernatural causes cannot, and hence presuming that an event has a supernatural cause for methodological purposes halts further investigation.
For the purposes of this discussion, I’m not going to be too insistent on particular definitions, but it seems to me this captures the essence of naturalism: “More simply, it [naturalism] is the denial of the existence of supernatural causes.”
Personally, I’d be on the side of naturalists or at least agnostic if I felt the origin of life question were satisfactorily resolved. So although I have sympathy for the naturalistic viewpoint, I find insistence on it too closed-minded. I don’t think reality operates in a completely law-like, predictable fashion, it only does so mostly, but not always.
The word “natural” can be equivocated to death and is often equated with “ordinary” or “typical” when it should not be. So if someone insists that naturalism is true but wishes to also be fair with the facts and avoid such equivocations, when they comment on the origin of life, they might say:
The origin of life was an atypical and unique event far from ordinary expectation, but many of us presume it happened naturally since supernatural events are not observed in the lab.
That would be the an accurate way to characterize the state of affairs, but this not what is usually said by advocates of naturalistic origins of life. Most origin-of-life proponents insinuate that the origin of life event was not terribly extraordinary, that OOL fits well within “natural” expectation, even though by accepted laws of physics and chemistry and current knowledge, such an event violates the ordinary (dare I say “natural”) expectation that non-living things stay non-living.
Turning to evolution, if someone insists on naturalism, but is at least fair with our present day knowledge, they might say:
It is NOT typical for something as complex as an animal to emerge from a single-celled organism, but we presume it happened naturally since animals share some DNA with single celled creatures.
Again, that would be the an accurate way to characterize the state of affairs, but this is not what is usually said by advocates of naturalistic evolution of life from the first cell. Evolutionists insinuate that the necessary events to evolve an animal from a single cell must not have been terribly extraordinary because animals and single-celled creatures share some similar DNA — the idea is insinuated even though it is a non-sequitur because something can share DNA via extraordinary or atypical events, at least in principle.
Darwin and his supporters argue that most evolution of complex function proceeded via a mechanism which Darwin labeled “natural selection”. However, if Darwin’s claims actually entail highly atypical events rather than ordinary ones, then his label of “natural selection” for how things evolved would be a false advertising label. If major evolutionary changes require highly atypical events, then “highly atypical events almost indistinguishable from miracles” would be a far more appropriate label for Darwin’s proposed mechanism of evolution. Instead, Darwin’s label of “natural” is presumptuous and unproven at best and completely false at worst. For all we know, natural selection prevents major evolutionary change. Michael Lynch points out:
many genomic features could not have emerged without a near-complete disengagement of the power of natural selection
opening, The Origins of Genome Architecture
Many? How about most? No one knows for sure, and thus Darwin’s label of “natural” for “natural selection” is presumptuous. For all we know the correct theory of evolution could be “evolution of significant novel forms by highly exceptional events”.
Animals and single-celled creatures share some DNA, but from all that we know, the transition from single-celled creatures to something as complex as a multi-cellular animal is highly atypical and so far from natural expectation that something of that order of change might likely not happen again in the history of the universe.
If naturalism can accommodate any atypical or extraordinary event as a matter of principle, no matter how improbable, then naturalism can accommodate events that would otherwise be indistinguishable from miracles.
Whether there is a theological dimension with atypical events is a separate question. Can there be an event atypical enough that it warrants supernatural explanations? That’s a philosophical question with probably no formal resolution.
Proponents of naturalistic emergence of biological complexity desperately pretend the sequence of necessary events are not atypical, but rather within the realm of ordinary expectation. Hence they try to render the question of supernatural origins as moot as the question of whether supernatural causes are needed to make ice melt on a hot day.
But imho, efforts to characterize emergence of biological complexity as “not that out of the ordinary” are failing. The more we learn of life’s complexity the more it seems highly atypical events were involved to create them. Perhaps these events were so atypical that they are virtually indistinguishable from miracles of supernatural creation.
I’m certainly not alone in those sentiments:
If we do not accept the hypothesis of spontaneous generation, then at this one point in the history of evolution we must have recourse to the miracle of a supernatural creation
Ernst Haeckel, 1876
Pasteur’s experiments and those followed from 1862 disproved spontaneous generation. Ernst Haeckel’s 1876 quote shows how false ideas like spontaneous generation die a slow death. Haeckel’s quote symbolizes how naturalism seems inherently uncomfortable with anything that suggests a highly atypical event actually happened somewhere in the past.