That topic, dear readers, is religion.
As I see it, there's four areas of concern within the topic, and I'd like to talk about them all.
First is the metaphysical aspect. This is the obvious one, but also the least relevant. Very few religious people, in my view, believe in a deity as a straightforward objective reality. At some point, people clearly did, but I suspect that this belief is holding on as little more than a formula. Anyone who seriously believes there's some sort of super-being outside normal space and time -- who doesn't take it as a metaphor or an abstraction or a moral ideal or some such -- is so deeply irrational that they should probably be kept away from sharp objects. That said, it's a fun point to play with because it sets the stage for pointing out the problems with the other aspects of religion; the metaphysical aspect is so obviously screwed up that starting with it gives a bit of a rhetorical edge to the later points.
Second, there's the epistemological issue. This is, simply, the problem of faith. "Faith" can be a weasel word, used by cowards to insulate some cherised beliefs from rational scrutiny. In that sense, faith isn't worth talking about because it's just a disavowal of responsibility for one's beliefs, and a refusal to engage seriously with the beliefs of those who disagree with you. There are, however, other senses of faith which are worth taking more seriously. For example, Kant's sense of rational faith, applied to the things that one can choose to believe in but never really know, for they lie outside the reach of experience (and, we could add, logical inference), and thus are literally unknowable. There is no proof for them, but also no proof against them, and thus one can only have faith in them. That sort of thing is an interesting attitude, and it's worth considering where it goes wrong.
Third, there's the moral issues. Many people rely on their religious beliefs to provide them with moral teachings. This is a basically juvenile approach, pushing responsibility for what one does and says onto some external force which (see point one) doesn't actually exist. But not only does religion teach us to be dependent for our moral views, it also warps us by eliminating or degrading our sense of human dignity, leading us into a sort of slavery. And religion also inculcates a list of vices which is pretends are actually virtues, modesty and humility among them.
Finally, there are political issues. This requires reading "political" broadly; the issue worth talking has nothing to do with, say, the US Catholic bishops taking shots at Obama for daring to say that health insurance should cover contraception. No, this is political in the sense of communal, of involving relations between people. It's probably the strongest argument in favour of religion that it provides people with a community, devoted to some sort of common purpose, many of which purposes are justifiably considered good. However, I suspect that there's very little that's actually religious here. That is, while it is true that groups can be good, and common purpose can be good, it's not true that these are necessary, nor is true that religious communities are a necessary or even preferable form of political unit.
So, stay tuned. This should be fun, at least for me. If it goes well, I may throw things together, tighten and edit them up a little, and e-publish it on Amazon or something as a little experiment in e-publishing. I'm not at all convinced that one can make a living publishing things any more, but it might be possible to at least make some pocket money.