An example: a gluttonous man will eat quite a lot because he desires to eat and he thinks eating will make him happy.
Most individuals can agree that gluttony can have harmful consequences and that, if one engages in gluttonous behavior with a desire to be happy, there may be unintended consequences to such behavior that lead to unhappiness or sickness. Of course, to call it morally wrong to be a glutton is different than calling it a lack of prudence or wisdom. Smoking cigarettes or eating fatty foods are not immoral, in the minds of most people; unhealthy, yes.
I’m not even confident that a virtue ethics could get one to the designation of immorality. We might say, common sensically, that someone who has no discipline – say, to prevent from overindulging – lacks character or lacks the “virtue” of discipline. Still, most of us don’t say he’s immoral in the sense of “he’s a bad person.” In this understanding of things, of course, the virtue of discipline is not an abstraction that has no connection with human wants and desires. In this case, virtue is a discipline because it would keep him healthy and fit – feeling better in body and mind; living longer, perhaps.
I think common ground breaks down most severely in precisely the example that seems of great importance to Feser, namely the proper use of one’s sexual organs. You see, with gluttony, we don’t just say “gluttony is inherently wrong” – in fact, most
do not say that. Instead, they say, “gluttony leads to obesity, which leads to ill health.” Thus, they give a concrete reason why gluttony is not desirable, including for the glutton himself. They do not make an appeal to what
nature desires, intends, or purposes.
In the case of insistence on the proper use of one’s sexual organs, it is not easy to demonstrate harm, in the way that one can demonstrate harm related to overeating, binge drinking, anorexia, drug use, or something like self-cutting. Does it ruin the health of the body? Potentially – but, then again, almost anything could ruin the health of the body. So it does not, in and of itself, ruin the health of the body; unlike gluttony or alcoholism, it is not
by definition immoderate.
If everyone engaged in it, never using the sexual organs to procreate, would the human race become extict? Yes, and that would be an example of harm. Yet celibate individuals, who do not use their sexual organs at all (presumably) would also create an extinct human race, if their behavior were the universal rule. As for those who “misuse” their sexual organs, they could both engage in non-procreative behaviors
and, at some point, procreate, and thus the non-procreative behavior could not be demonstrated to be harmful or
undesirable (again, with gluttony, it does not take much to convince someone of the
undesirability of such behavior, upon rational reflection).
But if
all you have is respect for what you understand to be the natural order of things – with no demonstrable harm, just the insistence that one
ought to respect nature’s rules – as one understands them – then one is asserting the faith that nature imposes moral obligations on us, even when violating nature causes no demonstrable injury to either
our desires, or to the
desire of others. And this is what “the world” does not understand and, indeed, has no faith or conviction about.
Jefferson is stating that the pursuit of happiness (which is not defined and has no ontological basis) is a self-evident right.
What is interesting is that Jefferson does not posit a
right to happiness, only a right to
pursue happiness. But I think he understands that what he calls a natural right is actually a social right, and he asserts it to be self-evident. Well, if it is a social right that you are talking about, then asserting it to be self-evident does makes it a
de facto reality (since, as far as society is concerned, which is man-made, human beings make the rules).
It’s true that he invokes the Creator, though he may have been seeking common ground between Deists, Trinitarian Christians (such as Anglicans) and Unitarians. I don’t mean to put words into Jefferson’s mouth but, if one understands his idea in terms of a “social contract”, then he doesn’t
need to ground civil rights ontologically (if such a thing were possible

).
That does not mean that life is not preferable; living things generally live until they succumb to natural causes.
I agree, but not based on what I think nature wants or doesn’t want. In the long view, everything in nature is indeed oriented towards death. Where I think one resolutely rejects this reasoning is by relying on human desire, not on visceral desire but on desire aided by reason, such as “I desire pleasure and long life; I also desire to eat food that tastes the best; however, if I eat food
only considering what gives my palate the most pleasure, I may undermine my goal of pleasure and long life.” Again, what nature has ordered or not ordered is besides the point, according to this thinking. If going against nature causing suffering or the thwarting of one’s desires – the wisdom and prudence that wants to avoid misery or shortened life – then one follows nature. But if going against nature has no discernible consequences – no demonstrated harm, even upon reflection – then one doesn’t take the extra step of saying that one is going to obey nature…for nature’s sake

And this is where I think the belief in final ends – such as Feser defends it, vis-a-vis the purportedly proper use of one’s sexual organs – loses most people. Of course, one is free to obey whatever moral dictates in nature one discerns, even when a violation of those dictates causes no demonstrable harm to human interests (either to self or others).