Can you give me an example of a complete theory?
History shows that all scientific theories change over time, as new evidence, observational capabilities, and understandings come into play. The obvious example is the transition from the geocentric theory to the heliocentric theory, and beyond via Newtonian mechanics and Relativity theory. In that sense no scientific theory is ever "complete."
The remarkable thing about Darwin's theory is it does not change; after 150+ years, it is still just as Darwin proposed it. It seems remarkably resistant to modification based on new evidence, observational capabilities, and understandings. IOW, it appears to be strikingly "complete." And yet on the other hand....
You quoted my dearest sister in Christ, Alamo-Girl:
The theory of evolution is incomplete. Darwin never asked or answered "what is life v. non-life/death in nature."I agree with her assessment. If Darwinism is a biological theory — biology being the study of life per se — Darwin's theory should address its subject matter, life. It should answer the question: What is it about living systems that makes them different from non-living systems in nature?
Both rocks and rabbits have the same material basis. What is it that causes them to be different orders of being altogether?
But Darwin's theory does not ask this question. It takes life "for granted," and goes about telling how life "speciates."
It doesn't tell us what life is; essentially, it only tells us what life "looks like," and how life forms change over time — blindly, randomly, as it were "accidentally."
Under the scenario "random mutation + natural selection," what you have is one material system in nature (an organism) undergoing mutational change, with another material system — nature, which is itself changing all the time ("evolving") — "locking" in changes in the organism that are beneficial to its survival and future reproductive capability. It is not at all clear to me by what principle the second material system (nature, itself subject to "random change") "knows" anything about the survival prospects of the first material system.
This is not a situation of "turtles all the way down". This is a situation of "accidents all the way down."
But if everything in nature is accidental — and therefore pointless, just a case of "stuff" happening — then what can we really say about it? Science doesn't deal with "accidents." It deals with discovering the bases of uniform, universal laws to which the natural world is subject.
So if all you can say about species change is that it is "accidental" — What kind of a scientific statement is that? "Accidental" to WHAT?
Which is why the more I look into it, the more I suspect that Darwin's theory is not really "scientific" — not in the way of, say, physics, which "allows" its theories to change as new insights and information warrant.
Yet it seems biologists are quite content with it; but not so much the physicists and mathematicians (including complex systems theorists and information theorists). Some of the latter see what's "missing" from Darwin's theory.
But most biologists nowadays (it seems) are highly resistant to the idea of physicists and mathematicians invading their "turf." In response to such interlopers, the great evolutionary biologist Ernst Mayr proposed that biology should be regarded as a "sovereign science" in its own right, on an equal par with physics, just not subject to the same rules as physics.
From which I gather that biologists will go to extraordinary lengths to maintain the "credibility" of Darwinian evolutionary theory — in the face of mounting criticisms from other sectors of the science community.
Perhaps you think I'm straining on a gnat here, dear tacticalogic. But what I understand myself to be doing is searching for the logical basis of Darwin's theory; and so far, I haven't found it.
Sorry to run on so long in answering your simple question. Thank you for asking it.