Long ago (I don't remember the source) I read an interesting thought: that people who speak about great ideas or strong emotions are probably intelectually and emotionally pretty weak, and when they get any result in such area, they are overwhelmed by the contrast. (It's like Dunning-Kruger on steroids.)
For example a smart person will have dozen smart ideas every day, so "having a smart idea" is no big deal for them, it's life as usual. Even if they find something extraordinarily interesting, they have a large reference class, so instead of greatness of the idea, they will speak about specific details that make this idea interesting.
On the other hand, when a rather dumb person hears a non-trivial idea and understands it, it is a shocking experience, a unique uncomparable thing. So the person will treat it as the greatest idea ever, the dividing line between stupid and smart, and will be obsessed about it.
Analogically, if a person with supressed emotions or mostly negative emotions suddenly falls in love, they will perceive their emotion as overwhelming, unique in the whole universe, unrepeatable. A person with a larger emotional scale would see the same emotion as a point in a continuum, so there is e.g. smaller chance they would do something stupid if their love is not reciprocated. The former person would (by a mind projection fallacy) think that the latter person's feelings are much smaller, because the reactions are less dramatic.
So maybe the same effect is at play here -- people who never thought too much about morality suddenly understand some moral rule, and (their interpretation of) it immediately becomes the moral rule, the dividing line between immoral and moral. (And if the rule is not based on emotions or traditions, it is convenient to label it as "utilitarian".)
That's an interesting thought. On the ideas, the other issue is that e.g. with certain fairly advanced mathematics, fuzzy and inaccurate understanding may easily be more amazing than any coherent understanding can ever be; the condition that is normally quite short lived if one has sufficiently thorough understanding of base level concepts and can study the idea formally, but this condition can be perpetual otherwise. Same can happen with morality.
I recently learned that a friend of mine, and a long-time atheist (and atheist blogger), is planning to convert to Catholicism. It seems the impetus for her conversion was increasing frustration that she had no good naturalistic account for objective morality in the form of virtue ethics; that upon reflection, she decided she felt like morality "loved" her; that this feeling implied God; and that she had sufficient "if God, then Catholicism" priors to point toward Catholicism, even though she's bisexual (!) and purports to still feel uncertain about the Church's views on sexuality. (Side note: all of this information is material she's blogged about herself, so it's not as if I'm sharing personal details she would prefer to be kept private.)
First, I want to state the rationality lesson I learned from this episode: atheists who spend a great deal of their time analyzing and even critiquing the views of a particular religion are at-risk atheists. Eliezer's spoken about this sort of issue before ("Someone who spends all day thinking about whether the Trinity does or does not exist, rather than Allah or Thor or the Flying Spaghetti Monster, is more than halfway to Christianity."), but I guess it took a personal experience to really drive the point home. When I first read my friend's post, I had a major "I notice that I am confused" moment, because it just seemed so implausible that someone who understood actual atheist arguments (as opposed to dead little sister Hollywood Atheism) could convert to religion, and Catholicism of all things. I seriously considered (and investigated) the possibility that her post was some kind of prank or experiment or otherwise not sincere, or that her account had been hijacked by a very good impersonator (both of these seem quite unlikely at this point).
But then I remembered how I had been frustrated in the past by her tolerance for what seemed like rank religious bigotry and how often I thought she was taking seriously theological positions that seemed about as likely as the 9/11 attacks being genuinely inspired and ordained by Allah. I remembered how I thought she had a confused conception of meta-ethics and that she often seemed skeptical of reductionism, which in retrospect should have been a major red flag for purported atheists. So yeah, spending all your time arguing about Catholic doctrine really is a warning sign, no matter how strongly you seem to champion the "atheist" side of the debate. Seriously.
But second, and more immediately, I wonder if anybody has advice on how to handle this, or if they've had similar experiences with their friends. I do care about this person, and I was devastated to hear this news, so if there's something I can do to help her, I want to. Of course, I would prefer most that she stop worrying about religion entirely and just grok the math that makes religious hypotheses so unlikely as to not be worth your time. But in the short term I'd settle for her not becoming a Catholic, and not immersing herself further in Dark Side Epistemology or surrounding herself with people trying to convince her that she needs to "repent" of her sexuality.
I think I have a pretty good understanding of the theoretical concepts at stake here, but I'm not sure where to start or what style of argument is likely to have the best effect at this point. My tentative plan is to express my concern, try to get more information about what she's thinking, and get a dialogue going (I expect she'll be open to this), but I wanted to see if you all had more specific suggestions, especially if you've been through similar experiences yourself. Thanks!