Some final thoughts:
I think the value of the Rambam/Ramban’s position is especially significant for those involved in kiruv. The truth of Torah becomes justified because of its correspondence to other already accepted values, e.g. our society accepts humane treatment of animals as a value, and if it can be shown that the Torah subscribes to the same value, Torah is validated. Precisely because the system is reductionist it is easy to “sell”. The only caveat I have is I am not sure how one distinguishes explanation from apologetics; believers often use the former label and skeptics the latter for the same ideas.
A comment asked why I take such a dim view of reductionism – don’t we need health, ethics, social law, etc.? A Torah that fulfilled those needs is one whose necessity is proven! I find that argument very hard to swallow because the same ends can be achieved via different means. The US Constitution does a good job of setting up an ordered society – why are the Torah’s laws better? The movement toward organic food shows great concern with what and how we eat – why do I need the details of kashrus? In fact, this is precisely the argument of reformers, e.g. see this article. Using the ends to justify the means only begs the question of why we cannot satisfy those same ends using more “modern” or appealing methods.
One critique that runs through the comments is that I am painting extremes – wouldn’t the Maharal agree that there is an economic utility to usury laws, or wouldn’t the Rambam agree that there is a spiritual dimension to certain mitzvos? I agree! But the question is what is cause and what is consequence.
The question of defining women’s role in Judaism illustrates another significant difference between these approaches. An example: Why are women exempt from mitzvos aseh she’hazman gerama? Some (Avudraham) argue that the duties of the home come first; women are freed from mitzvos to devote themselves to household chores. That rationalization presupposes a specific role for women as a value even higher than the service of G-d and reads that into the halachic structure. Going back to the Maharal’s analogy to a tree, one might suggest that just as there are oak trees and maple trees with different botanical needs, the same holds true of the spiritual needs of our different souls, and hence the differing obligations in mitzvos. If the Torah wanted to define social roles, it could have taken a much more direct route to doing so. My wife prefers the latter type of explanations as it removes halacha from externally imposed social values, yet, many a person has been drawn to Judaism precisely because they see strongly defined social roles as “family values” that they can identify with. Chacun a son gout!
Two quotes: 1) A critique a correspondant offered to my BIL: “What difference could it have rationally towards my moral refinement to discuss a stirah in rishonim in zevochim???? Or offer a lmudische disscetion of a machlokes.” 2) A response from another blog when I asked whether there was value to mitzvos performed in ignorance of their supposed reasons: "So in answer to your first question there is no value other than training or the idea of mitoch shelo lishma ba lishma." Whether you are sympathetic to the first critique or the second statement I think depends on whose side in this whole debate you are drawn to.