I'm saying he's making an advance in ethical thinking in pointing out how is/ought frequently get conflated as if they have the same import.
I'd say it's question begging sophistry (in precisely the way Plato frames sophistry). To make the distinction is to have already presupposed that there are not facts about what is good. Now, thanks to the theological issues I mentioned earlier in this thread, such a position was already common by Hume's time. It went along with fideism and a sort of anti-rationalism and general backlash against the involvement of philosophy in faith (and so in questions of value), all a century before Hume.
Hume argues to this position by setting up a false dichotomy. Either passions (and we should suppose the appetites) are involved in morality or reason, but not both. Yet I certainly don't think he ever gives a proper explanation of why it can't be both (univocity is a culprit here of course). For most of the history of philosophy, the answer was always both (granted, Hume seems somewhat unaware of much past philosophy, and his successor Nietzsche seems to get his entire view of it from a particularly bad reading of the Phaedo and not much else from Plato).
It's sophistry because it turns philosophy into power relations and dominance. Hume admits as much. "Reason is, and ought only to be the
slave of the passions” (T 2.3. 3.4)." This is Socrates fighting with Thacymachus, Protagoras, and that one guy who suggests that "justice" is "whatever we currently prefer" in the Republic (his name escapes me because he has just one line and everyone ignores him, since, were he right, even the sophists would lose, since there is no need for their services when being wrong is impossible). The only difference is that now the struggle is internalized. This certainly goes along with Hume (and Nietzsche's) view of the self as a "bundle of sensations" (or "congress of souls"). Yet, Plato's reply is that this is simply what the soul is like when it is sick, morbid.
Just from the point of view of the philosophy of language it seems pretty far-fetched. Imagine someone yelling:
"Your hair is on fire."
"You are going to be late for work."
"You're hurting her."
"Keep doing that and you'll break the car."
"You forgot to carry the remainder in that calculation."
"You are lying."
"You didn't do what I asked you to."
"That's illegal."
"You're going to hurt yourself doing that."
"There is a typoo in this sentence."
...or any other such statements. There are all fact claims. They are all normally fact claims people make in order to spur some sort of action, and this is precisely because the facts (generally) imply oughts. "Your hair is on fire," implies "put the fire on your head out." And such an ought is justifiable by the appetites (desire to avoid pain), passions (desire to avoid the opinions of others related to be disfigured or seen to be stupid), and reason (the desire to fullfil rationally held goals, which burning alive is rarely conducive to).
At least on the classical view, the division is incoherent. There are facts about what are good or bad for us. To say "x is better than what I have/am, but why ought I seek it?" is incoherent. What is "truly good" is truly good precisely because it is desirable, choice-worthy, what "ought to be chosen" (of course, things can merely appear choice-worthy, just as they can merely appear true). Why should we choose the most truly choice-worthy? We might as well ask why we should prefer truth to falsity, or beauty to ugliness or why 1 is greater than 0.
For the second, could you perhaps say briefly how analogous predication would apply here, in the case of what looks like two usages of "good"? It's quite possible I don't yet understand how that would work.
Short answer: just as the measure of a "good car" differs from the measure of a "good nurse" (the same things do not make them good) the measure of a "good act" or "good event" will differ from that of a "good human being" (and in this case the former are not even things, not discrete unities at all, which is precisely why focusing on them leads to things like analyzing an unending chain of consequences).
I can share a long (but still cursory) explanation when I get to my PC, but the basic idea is that "good" is said many ways. The "good" of a "good car," a "good student," and a/the "good life" are not the same thing. Yet a good car certainly relates to human well-being, as any
More specifically, to make these sorts of comparisons/predications requires a
measure. This is in Book 10 and 14 of the Metaphysics I think (and Thomas' commentaries are always helpful). Easiest way to see what a measure is it to see that to speak of a "half meter" or "quarter note" requires some whole by which the reference to multitude is intelligible. Likewise, for "three ducks" to be intelligible one must have a whole duck as the unit measure.
For anything to be any thing is must have some measure of unity. We cannot even tell what the dimensive quantities related to some abstract body are unless that body is somehow set off from "everything else" (i.e., one cannot measure a white triangle on a white background—there are a lot of interesting parallels to information theory in St. Thomas).
I think I already explained Plato's thing about how the "rule of reason" makes us more unified and self-determining (self-determining because we are oriented beyond what already are and have, beyond current beliefs and desires). Next, consider that organisms are proper beings because they have a nature, because they are the source of their own production and movement (not absolutely of course, they are not subsistent). Some non-living systems are self-organizing to some degree (and stars, hurricanes, etc. have "life cycles").The scientific literature on complexity and dissipative, self-organizing systems is decent at picking up on Aristotle here, but largely ignores later Patristic, Islamic, and medieval extensions.
Yet non-living things lack the same unity because they don't have aims (goal-directedness, teleonomy) unifying their parts (human institutions do).
The goodness for organisms is tightly related to their unity. In general, it is not good for an organism to lose its unity and die. "Ok, but sometimes they do this on purpose, bees sting and stinging kills them."
Exactly! Because what ultimately drives an organism is its goals. Brutes can't ask what is "truly good" but they can pursue ends that lie beyond them. And note, bees sacrifice themselves because they are oriented towards the whole, just as Boethius and Socrates do. This is because goodness always relates to the whole (because of this tight relationship with unity).
So to return to how goodness is said in many ways, goodness is said as respect to a measure. The measure of a "good house" is a house fulfilling it ends (artifacts are a little tricky though since they lack intrinsic aims and essences; people want different things in a house). The measure of the "good duck" is the paradigmatic flourishing duck (no need to posit independent forms existing apart from particulars here BTW).
Because equivocity is so rampant in our day, essentially the norm, let's not use "good person." Let's use "excellent person." The excellent person has perfected all the human excellences, the virtues. "It is good for you to be excellent." Or "it is excellent for you to be good." In either case the measure for "you," as a human, is human excellence, flourishing.
But because reason is transcedent, we can aim at "the best thing possible," which is to be like God. God wants nothing, lacks nothing, and fears nothing. Yet God is not indifferent to creatures, for a few reasons but the most obvious is that the "best" lack no good, and love is one of these.
God can also just be the rational limit case of perfection, having the best life conceivable. We might miss much in this deflation, but it still works.
We want to be the best person and live the best life possible. At the same time, goodness always relates to the whole, to unity. No doubt, we can usefully predicate "good" of events, but this goodness is parasitic on things. There is no good or bad in a godless world without any organisms (anything directed by aims). You can't have goodness without wholes with aims.
The predication vis-á-vis some good event has to be analagous because nothing can be "good for an event." The event is good or bad for some thing, according to its measure.
In the 19th century there were many competing theories of heat and electromagnetism. There was phlogiston, caloric, aether, etc. Are we best of returning to the specific, isolated theories, or looking at how what is good in each can be unified?
You might say "but the natural sciences are different, they make progress." And I would agree. It's easier to make progress when one studies less general principles. Yet they don't always make progress. Recall the Nazi's "Aryan physics" or Stalin's "communist genetics." The natural sciences can backslide into bad ideas and blind allies. It is easier for philosophy to do so.