This is the view commonly called Darwinism and was indeed the position held by Charles Darwin himself.
On this model there's no room nor need for any supernatural intelligence to act at any stage in the process. Darwinians hold that in principle all of biology can ultimately be explained by the laws of physics and chemistry and the initial conditions of the universe, all of which just happen to be what they are.
The second option is that however life may have first arisen and diverged into the manifold forms we see around us, it could not have occurred solely through natural processes. A supernatural intelligent agent must have been involved. The manner of that involvement is controversial among those who hold this view, but there's nevertheless broad agreement among them that apart from that involvement no life would have ever appeared on earth or anywhere else.
Protein chemist Doug Axe, the author of Undeniable: How Biology Confirms Our Intuition That Life Is Designed elaborates on this second option in a piece at Evolution News. In a dialogue with a friend Axe says:
I understand why you, as a theist, are okay with God having created life either by divine fiat or by wielding natural forces the way a sculptor wields a chisel. So am I! The problem is that neither of those options is on the table in the biology departments of the major research universities. There, chance and nature (both completely blind) are the only options on offer.This is the fundamental divide in the debate over evolution. The critical disagreement is not between special creationists and evolutionists, nor between theistic evolutionists and intelligent design theorists. The fundamental debate is between those who believe life to be solely the product of an unguided, purely naturalistic process and those who believe that an intelligent agent is somehow necessary to explain what we find in the biosphere.
As understood by their main proponents, Darwinism and design are most emphatically not compatible...: proponents of design hold that living things cannot have arisen by ordinary natural processes, whereas Darwinists hold the opposite view. I understand the appeal to giving a nod in both directions, but that doesn’t resolve the contradiction. Evolution is either unguided (in which case it doesn’t work) or overwhelmingly dependent on guidance (in which case it isn’t natural). It can’t be both!
Axe goes on:
Keep in mind that the improbabilities I’m referring to are not at all restricted to the origin of the first bacterial cell. For example, hummingbirds exhibit high-level functional coherence that is entirely absent from bacteria.In other words, even if one assumes that somehow, against astronomical odds, a primeval, self-replicating cell were to have formed, eventually giving rise to all creatures extant throughout the history of earth, the crucial metaphysical question is still whether chance, matter, and physical law can, by themselves, provide a sufficient account for this history or whether the evidence is better explained by also invoking purposeful engineering.
According to the argument I put forward in [my book] Undeniable, the probabilistic implications of this simple observation make it impossible for accidental processes acting on bacteria to have produced anything comparable to hummingbirds, whether on Earth or on any other planet.
...Darwin offered first and foremost a mechanism which he thought explained the origin of all modern life from some simple first life. I’m saying he was comprehensively wrong about that .... Specifically, I’m saying we can be very confident that the blind natural mechanism he appealed to can’t possibly be the inventor of new forms of life.
His other big contribution was the idea of all life being related by common descent — Darwin’s tree of life. That idea is separable from the question of mechanism, and I’m very willing to consider its merits (in fact, this is one focus of my current work). Undeniable takes no position on common descent.
Axe's book Undeniable makes a powerful case that the evidence is overwhelmingly in favor of the intelligent agent view unless, because of an apriori philosophical commitment to naturalism or atheism, one simply refuses to consider it.
