Apologies in advance for what is a lengthy response. Perhaps we should narrow the discussion to make it more manageable. I've highlighted the points that I think are essential, so that you needn't feel compelled to respond to everything I've said.
Oh dear. Let’s return to your hut example courtesy of von Wright:
I want to make the hut habitable.
Unless I heat the hut, it will not become habitable.
Therefore I must heat the hut.
And my semantic variation which to my mind results in the same outcome:
I want to make the hut habitable.
Unless I heat the hut, it will not become habitable.
Therefore, because I want the hut habitable, I need to heat the hut.
In short, an “ought” statement is not required to attain the same end. One can infer from accumulated knowledge of what makes huts habitable (i.e. heating) that one needs to heat the hut. The difference is between your assumed premises (unless I heat the hut, it will not become habitable) and the tested knowledge that heated huts are more habitual than non-heated huts. I might add that philosophy does not have the mechanism to determine what makes the hut habitual (i.e. heating), whereas science does.
Let's start by first noting that von Wright's syllogism is not a philosophical argument at all. It represents the sort of practical deliberation that every person uses in selecting what he ought to do (in the context of a necessary means, at least).
Second, let's note that
every single person has explicitly stated that the means-end relation that occurs in a syllogism may well come from science and that this is a good use of science. The means-end relation expresses a belief about causality, and such beliefs are reliable if they are well-justified by science.
Third, let's note that, despite saying that, it is stupid to pretend that we need science to help us determine that huts need to be heated in order to be habitable or that lava may burn us or a million other things that you claim science provides us. Oh, science might tell us that the volcano is nearing eruption, a conclusion we might not reach without the careful observation and deduction science provides, but I'm pretty sure that I can see a hut isn't habitable without heat if it is in a temperate area. We don't allow silly statements like, "Without philosophy, there is no argument, because philosophy introduced logic," and we should not allow stupid claims like, "Without science, you wouldn't know that decapitation shortens one's expected lifespan."
Fourth, let's look carefully at your conclusion.
One can infer from accumulated knowledge of what makes huts habitable (i.e. heating) that one needs to heat the hut.
The use of the term "need" there is instructive. It expresses a practical necessity, i.e., is just another word that means "ought". You need to do this, because it is necessary to attain your end. No difference between that sense of "need" and the corresponding "ought" statement -- but you've said that science doesn't derive normative statements.
Fifth, you've said that your version of the argument is
inductive, with a descriptive conclusion (contradicting your justification in terms of the normative restatement above). But what does that mean?
All I can guess is this: Because of past observations, I recognize that I usually do what is necessary to attain my ends. Hence, I conclude that I will probably do so here. Right? That's what an inductive argument would look like, yes?
But this kind of argument does not provide any reasons to do something. It merely provides a prediction that I will do it. This is useless in a situation in which I am deliberating about what to do.
My question is not a non-sequitur. If you think morality has inherent value, which was my question, then it will affect your entire argument. So, again: “do think morality has inherent value, why?”
I want to focus on a couple of narrow points for now, and that point is irrelevant to me. I'm criticizing your argument, not putting forth an original argument as to the nature of morality.
My main interest right now are the following points:
(1) You claim that science does not derive norms (and I don't dispute this claim) but nonetheless science can provide practical arguments about what to do. Since deliberation about what to do is deliberation about appropriateness of action (i.e., normative), this is a contradiction.
(2) You claim that science does not derive norms, but nonetheless can provide a basis for morality, despite the fact that morality is also about appropriateness of action.
(3) You claim that morality, properly viewed, is not normative, although it is a code of behavior (again, a fundamentally normative concept).
You have entirely missed the point, namely WHY is it “good to act as the rules specify and bad not to” and WHY did we arrive at such rules? My answer: Conformity to rules of behaviour within a group is instinctive for social creatures such as us, because morals are derivatives of self-preservation and procreation and a consequence of natural selection.
You've said that science doesn't derive normative statements. Any system of rules of behavior is a system of norms. By your own declaration, science doesn't derive such claims.
Yes, I think science could give an account of how we have come to use this set of rules or that, but that's not what a moral theorist fundamentally wants. He wants to know what set of rules is a good set of rules, to what end should such rules tend. And science can only say that our sets of rules have (allegedly) tended towards social cohesion, not that this is a good aim. So science gives no justification for this set or that, unless an end has been selected.
Your answer would appear to be that morals have an inherent value, i.e. that they are true in and of themselves, rather than arising from our natural instincts. Is that what you think?
This is not a digression; it’s the core of the argument. ‘Morality is about social cohesion’. What else would it be? Codes of behaviour evolved for functional reasons, namely as a means of restraining individual selfishness and enhancing social cohesion, because the benefits of living in large cohesive groups are demonstrably greater than living alone without community support.
Not interested. For now, I'll grant that codes of behavior have evolved for functional reasons, but dispute whether this is reason enough to abide by or support such codes. That is, I'll grant the historical claim, but question whether this history is reason enough to think these rules are good rules.
When I say my benefit is improved, I'm taking the risk of penalty into account. Sometimes, the risk of penalty is negligible compared to the direct benefit of the transgression.
This is true regardless of how the rules of behaviour are arrived at.
Yes, I think so, too. That's why I wrote explicitly, "though that is, of course, a problem for realist theories in general, as well."
I think, therefore, that this is another digression, off the main point of our discussion. The problem of motivation to be moral when it's not in one's interest isn't limited to your theory of morality, and so needn't distract us here. Let's put the focus on the features that are specific to your claims here.
All you have to do is rephrase the “ought” statement thus: “If I want to survive the volcano I should flee”. What you are doing is drawing an inference (i.e. an act of reasoning from the factual knowledge or evidence the volcano will destroy me). And the reason I want to survive is because ‘survival’ is the dominant instinct of most life forms – ever tried to kill a mosquito? It doesn't need a normative argument for the mosquito to try and escape the swat.
Well, let's look at your rephrasing.
First, it still includes a normative component. You now have "should" taking the place of "ought", but the meaning is unchanged, so you haven't excised normativity.
Second, it is a conditional statement, in which the "should do X" part occurs in the consequent (i.e., it is what Kant called a hypothetical imperative). By itself, it does not motivate any action at all. Only if I recognize that the antecedent is true do I derive a motive to act, that is, "I should flee."
Now, if science actually tells me that I want to survive (because science tells me this is a drive that evolution has instilled in me), then science has just derived a bald-faced norm: I should flee. Contrary to your claims of science.
Of course, it is silly in the extreme to pretend that science tells me that I want to survive. On the contrary, I feel that desire intimately, without reference to any science texts. Indeed, if I felt the oppression of my troubles so acutely that I found death preferable to life at this moment, no number of scientific references would change my mind. Therefore, to complete the argument, so to speak, I reach for a premise which science does not determine for me:
I ask myself whether or not I desire this end, for which fleeing is a necessary means. If I do, then the hypothetical imperative necessitates that I flee, and if not, then it is irrelevant to my deliberations. As we can see, the move from hypothetical imperative to a motivation for action goes beyond any scientifically grounded claim.