This will, I think, be a slightly controversial, but also somewhat arid, post. Feel free to ignore it if you don't have an interest in controversial assessments of academic philosophy.
I was thinking earlier today of curious lacunae in philosophical literature. I think it was something I read about the contraception mandate, because my original thoughts were on philosophical discussions of contraception. Almost all bioethicists today, I would imagine, think contraception is "morally permissible," however they gloss that. Indeed, one of the standard criticisms raised against Marquis's anti-abortion argument -- which is usually the token anti-abortion argument that's considered respectable enough to take seriously -- is that it would make contraception wrong, too. (It wouldn't, for a number of reasons, but that's another argument.) But it's notably difficult to find any serious philosophical argument for this. You often get more general arguments that would suggest something or other about contraception, in feminist works. But close philosophical discussions of particular lines of argument for the claim that contraception is OK are actually quite difficult to find. For instance, the kind of argument for contraception with which I am far and away the most sympathetic is the class of voluntary motherhood arguments. You almost never find any discussion of them outside of occasoinal historical surveys, and sometimes as secondary issues in reproductive choice arguments (but 'reproductive choice' is a broader and messier term that covers quite a few things.) What's interesting is that it's actually pretty easy to find philosophical discussions arguing against contraception. There's Anscombe's Contraception and Chastity paper for instance (which actually as far as what the Catholic position should be is a much better anti-contraception argument than you usually ever find), and it's not difficult to dig up Catholic bioethics papers arguing against contraception. The discussion is entirely lopsided, and it's lopsided in the opposite way you'd expect. You can get more results on the pro-contraception side if you jiggle things a bit. You can find philosophical arguments that health care professionals should dispense emergency contraception regardless of conscientious objection issues, for instance; but what one notices if one looks closely is that contraception itself is rarely a significant issue in the argument -- they are almost always about general limits to conscientious objection, not about anything especially appropriate to contraception itself. Remarkably, the only times you usually get anything like a philosophical discussion of the permissibility of contraception is in discussions of abortion, and there the arguments are usually just to say that the moral issues concerning contraception are different (or sometimes the same).
I think there are other interesting lacunae; thinking about the lacuna with contraception arguments, I started thinking about abortion arguments. There are lots of those, on both sides, although you have to go to different places for them (but that's not surprising). But you get odd lacunae when it comes to individual arguments. For instance, the pro-choice argument I am most sympathetic to -- very sympathetic to, actually, since I think it raises an extraordinarily serious point that has to be faced by any acceptable pro-life view -- is the argument that one of the salient issues is that the embryo and fetus are part of the woman's body. Now, it's not difficult to see that this is a very, very popular argument, and I think it's so because it's actually a very good argument. Here and there you find pro-life arguments that argue that the embryo or fetus is not (relevantly) part of the mother's body; they aren't necessarily absurd, but they're nonstarters. There are are overwhelmingly good reasons, regardless of whether you are pro-choice or pro-life, to regard the embryo and fetus as part of the mother's body, even if you hold (as in fact I do, being pro-life myself) that they are not merely body parts. But close and serious philosophical discussions? Very rare, and the few that do are usually concerned more with the concept of self-ownership than abortion.
This failure to consider the nux of the dispute is, I think, a common pattern in the case of abortion. Almost all discussion of Marquis's arguments, for instance, could continue almost exactly as they do if abortion had nothing whatsoever to do with women -- they are all about whether killing is wrong because it deprives people of their future. The fact that abortion is the key case is almost accidental. Judith Jarvis Thomson's violinist case in A Defense of Abortion has had a lot of discussion, which is reasonable because like most of Thomson's work it is quite good, and is the sort of serious argument you would expect. But for most of the discussion that followed, again, it's almost accidental that abortion is there at all, and even when it is not, most of the discussion could proceed in the same way if abortion had nothing whatsoever to do with women. But all the arguments for abortion that have the most popular appeal are women-centered. And yet it is extraordinarily difficult to find philosophical elaborations of women-centered arguments for abortion as a choice, despite the fact that you'd expect them to be quite common. I suppose it could be the case that most people assume it's the default. (I am almost certain that that's the reason in the case of contraception.) But that's not a good reason for not discussing it explicitly; for instance, discussion might show that it needs to be more than a default, or that some other variation would make a better default. And an undefended default is a default the other side can treat as irrelevant and, on any contentious issue, will.
I want to make clear that I'm not saying that there are no discussions of the sort. There are; they're just scattered and difficult to find, and much more rare than you'd think they'd be if you didn't actually look. If you think I'm not quite judging things correctly, I invite you to look around yourself; you'll find that the serious philosophical discussions I mean are quite difficult to find, and many discussions that superficially are about them actually only use them in an incidental way. I also don't think contraception and abortion are the only cases; they just stand out because they are so contentious in public life that you'd think there would be better philosophical coverage of them than there actually is.
Philosophers chase their own interests; and their interests might well not coincide with the interests of non-philosophers. But I think there's a good argument that ethicists in particular, in addition to whatever interests they may have themselves, should be discussing the actual arguments that people actually make (or, to be more exact, arguments in those families, since the arguments people actually make will often tend to be loose, approximate, and summary versions of more sophisticated arguments). This is not to say that they never do -- you get great discussions of things like vegetarianism and animal rights in precisely this vein and (for instance) works on homosexuality, both for and against, often make an explicit point of having close discussions of popular arguments as well as whatever's academically fashionable. But if it's the case that ethicists should be doing this, I think there's also an argument that they should be doing it quite broadly across the range of public interest.
So I suppose this raises two questions.
(1) While I do try to keep a general sense of what's going on, obviously ethics is not my primary field. So am I just somehow missing the extensive philosophical discussions of these issues in their own right?
(2) What other fields are there in which close philosophical discussions are rare? What gaps are there? For a long time taxes and welfare were, although this has slowly gotten better; there are whole sections of the field that are still surprisingly sparse. Outside of business and medicine professional ethics seems to me to be sparsely discussed -- there are fascinating things involved in the ethics of professional fishing, and ethical fishing practices are constant issues of importance for fishing communities and the fishing industry, since long-term survival can depend on them. But I don't think there's much philosophical discussion of them at all, although they occasionally come up in general discussions of sustainability. Collections care is another field in which ethics is practically important that seems sparsely discussed by professional ethicists despite its importance to the public. I know that for my ethics course I always have difficulty finding materials for civil service ethics (which is the branch of government ethics I focus on) that actually focus on specific civil-service issues rather than very general conflict-of-interest issues. There's a lot on it -- most governments, including the U.S., have bureaus and departments of ethics that are constantly collecting information and writing up little reports on ethical issues in the civil service. But extensive philosophical discussion of this material is not usually to be had.
And, of course, one can argue that it's not just ethics that has this problem. I can think of half a dozen issues in philosophy of religion that are (1) important in greater public life, often to very large populations; (2) potentially interesting philosophical topics; and (3) hardly ever discussed. Things like ritual sacrifice, Sikh Guru consciousness, kashimono-karimono, the status of religious law, the relationship between conscience and worship, i'jaz al-Qur'an, indigenous religions, and mythology as a guide for practice are well outside the little treadmill of arguments most philosophers of religion discuss.