With all due respect, LeGrande, please tell me how you can isolate the idea of a biological "function" from the idea of "purpose." I'm not speaking here of someone's purpose (i.e., a conscious agent at work). That is not the issue. I'm just looking at the logical idea of purpose or goal (final cause) in a completely naturalistic setting.
A brief review of the classical Aristotelian causes:
The formal cause (eidos) is the pattern or design according to which materials are selected and assembled for the execution of a particular goal or purpose. For example, in the case of a Boeing 747, the blueprint (or schematic) would be its formal cause. This is the key “explanation” for the jet; for its construction materials and subcomponents would be only a pile of rubble (or a different jet) if they were not put together in the particular way its blueprint specified."The final cause is an end which is not for the sake of anything else, but for the sake of which everything [else] is." [Aristotle, Metaphysics, Book XII, Section 7.]The material cause is the basic stuff out of which something is made. The material cause of a Boeing 747, for example, would include the metals, plastics, glass, and other component materials used in its construction. All of these things belong in an explanation of the 747 because it could not exist unless they were present in its composition.
The efficient cause is the agent or force immediately responsible for bringing that material and that form together in the production of the Boeing 747. Thus, the efficient cause of the jet would include the efforts of engineers, materials fabricators, hydraulics specialists, and other workers who use the designated materials and components to build the jet in accordance with its specifying blueprint. Clearly the Boeing 747 could not be what it is without their contribution: It would remain unbuilt.
Lastly, the final cause (telos) is the end or purpose for which the Boeing 747 exists. The final cause of the jet would be to provide safe, reliable, comfortable air transportation for human beings. This is part of the explanation of the 747’s existence, because it never would have been built in the first place unless people needed a means of air transportation. [J. Drew and S. Venable, Don't Let Science Get You Down Timothy, p. 48]
We don't have to bring God or anything supernatural on-stage to speak of final causes. My point is they are already in Nature. Thus you are imbuing that term with a religious connotation that is not relevant. Final cause is a logical idea.
Contemporary science (i.e., the Newtonian Paradigm) wants to explain everything in terms of material and efficient causes only. Which is why I very strongly believe it has no method for addressing biological systems because in addition to material and efficient causes, organizational causes (so to speak) are at work as well. It seems to me organizational entailments invoke the very idea of formal and final causes. Which incidentally pertain to (fabricated) machines as well as (natural) living organisms.
My argument is not based on "finding" or "proving the existence" of God. I don't need to convince myself about a conviction I already have. All I'm trying to do here is to indicate certain intractable facts about biological organisms than cannot be explained in terms of material and efficient causes only.
[[We don’t have to bring God or anything supernatural on-stage to speak of final causes.]]
The naturalist endows nature with that role- despite hte fact nature is incapable of supernatural acts with purpose
Informaiton, and hte succesful communication of it within the whole metainformation system, screams out purpose, and it screams out intelligence- there simply is no way to seperate the need for intelliguence from the evidnece, nor is htere a way to relegate the purpose, the creation, the assembly, and the colloperation of all systems within life to nature- The whole heirarchal system of information speaks very clearly to the need for an intelligent organizer- just as viewing hte 747 would by someone who had never seen one before- with the myriad of complex irreducible parts in both life and the 747, one simply can not argue that natuire is capable such complex, highly integrated, and itnerdependent system arrangements- not logicvally anyway
and your definition of final cause
Lastly, the final cause (telos) is the end or purpose for which the Boeing 747 exists.
You can't separate 'final cause' from 'someone's purpose.' Unless you want to change your definition of final cause.
Thank you for your outstanding essay-post, dearest sister in Christ!