[Serious] Generally speaking, is philosophy a worthwhile subject of study?

[vulcanlogician]

I know that the case for divine command theory is weak.

Except that you probably haven't actually ruled out DCT. You have simply come to a place where your intuitions conflict with it.

And that is a bit of self-knowledge: that your intuitions don't agree with the consequences of DCT. But that alone isn't a reason to reject DCT. It may mean you simply have to change your intuitions about morality.

For example, the results of quantum theory are very counter-intuitive to most people (especially at the start). But that does not make them wrong. It simply means our intuitions are wrong.

The question is whether there is a standard from which we can test ethical theories and determine that they are wrong in some objective way. I am open to that as a possibility. But I have yet to see such. And that is why they don't form 'knowledge' and are still in the realm of 'educated opinion'.

No astronomer currently uses Ptolemy's system for understanding the solar system. It has been shown wrong. it isn't even a good approximation (unlike, say, Newtonian mechanics). Galileo made observations that show it to be wrong. But there are still people today who subscribe to DCT, even among educated ethicists.

Great point. And you saying that about QM really helps me see where you're coming from. QM is counterintuitive. But it's demonstrably true. In ethics, we can't really "demonstrate" that a counterintuitive thing is true. And, so, who's to say an ethicist's conclusions count as knowledge? We can only say that it conflicts with our intuitions.

Again, very good point and very good criticism. But you should realize how careful most philosophers are when parsing the arguments. No good ethicist says, "It conflicts with our intuitions and is therefore false." They rather say: "It conflicts with our intuitions, so there's that problem with X theory." Even scientists recognize that our intuitions can be useful in showing us what kind of observations and that counterintuitive claims require extra investigation. And, I did say Divine Command Theory is "weak"-- not "false." So hopefully I'm being a careful ethicist in that regard.

But we can say that DCT is false is some situations. If we know that God is a rational being with his own intentions, and we (somehow) know that God would never decree ethics arbitrarily, then we know divine command theory is false. That is enough to put it in front of the theists as a genuine challenge if they want to argue DCT. Because the theists claim to know those things about God. And if those things are true, it is a priori deducible that DCT is false.

I guess what I'm getting at is that people have all sorts of erroneous and illogical ideas about God, ethics, and the like. Even if philosophy can't produce knowledge that meets your (empiricist) criteria for knowledge, it still does a good job at eliminating shit that many people consider knowledge because they haven't thought things through properly. The philosopher doesn't snap off the judgment: "DCT is nonsense" because the philosopher, instead, wants to think about why DCT is nonsense.

It's a different field from physics. Because we aren't all staunch empiricists, we have different (but defensible) definitions of knowledge. Your categorizing of knowledge as "empirically demonstrable" or else "self knowledge" doesn't quite cut it with me. I think you are focusing too much on empirical confirmation as a criterion for knowledge. What about justified true belief? We can discuss the merits of justified true belief vs empirically confirmed data if you wish.

I kinda wished I hadn't used ethics as an example. Ethics has the problem of possibly needing to be rooted in our intuitions. I actually prefer an ethical theory that suggests precisely that. Although, like you, I'm suspicious of human intuitions enough to make me suspicious of the theory. Not all moral realism suffers from this problem, however, and some heavily principled theories say that "when our intuitions conflict with the principle, our intuitions are probably wrong." But (in either case) just like scientists, ethicists are more prone to see conflict with intuitions as provocation to examine the issue more closely, not as a reason to dismiss it entirely.