More seriously -First - I think it’s important in all sciences, and especially in the human sciences, not to move to “why” too quickly, before the “what” is well established — especially in the human sciences, because a partial what can be used to support all kinds of crazy whys.Second — the why in the human sciences is almost always going to be some kind of interpretation, and that interpretation is likely going to be heavily theory laden.With those principles in mind, the relevant passage in Mary Douglas is chapter three in “Purity and Danger: An Analysis of the Concepts of Pollution and Taboo”. I like this book a lot, but that doesn’t mean that I buy everything she says. (She also wrote a book specifically on Leviticus, but that book isn’t actually so relevant to this discussion). In another book, “Natural Symbols”, she talks a lot about boundary maintenance, and I had a false memory that she used boundary maintenance in “P&D”, but I was wrong. She argues something more like a standard structuralist line. In brief, and without going into a lot of detail, she argues that the categories in Leviticus reflect and symbolize a general cosmology; for all the detail you have to read the whole book, but it has to do with her general discussion of pollution and dirt and holiness. In Hebrew, she says, the word usually translated “holy” really means “set apart” — so setting things apart has a particular importance in Hebrew religious thought. And she connects all this with a wider comparative account of pollution in various societies.+But as I said, Marvin Harris says that this is all wrong. In “Good to Eat: Riddles of Food and Culture” he says that food rules always turn out to make good economic sense.+So each argument sits within a theory — Douglas’ argument sits within a structuralist theory, Marvin’s argument sits within his cultural materialist theory. You pay your money and you take your choice. I find good in each. Harris’ argument about food makes sense to me in general, but its weakness here is that he doesn’t take the rest of the rules in Leviticus into account. Douglas’ argument makes sense of the whole of Leviticus, but it’s hard to attach it to anything real — or material.+One point Douglas makes is that if you are going to ask what’s up with the laws in Leviticus, you should also be prepared to ask what’s up with the laws in your own culture. Often it’s hard to see the rules in your own culture, because you swim in them, but she argues that in fact we have a whole set of rules about hygiene and dirt and that these rules don’t always make a lot of “scientific” sense. I would certainly say that our culture has a lot of anxiety about food, and it’s worth asking why.+I don’t know if any of that is of any interest. I recommend both “Purity and Danger” and “Good to Eat” — they’re lots of fun, no matter what you think of them in the end.