In debates in ethics (among new and old natural law theorists for instance) one problem that comes up is the incommensurability of certain types of goods. What this means is that it doesn't seem that in general we can even weigh certain goods against others (for example, say, aesthetic experience and friendship). An apparent problem for utilitarians and consequentialists of various stripes, among others.
I'm not sure how much this has to do with that, but it struck me now as I'm working in my personal library of books how much incommensurability considerations affect me on a concrete, everyday level.
I was sitting here looking over a syllabus, and I realized I will have a week-long break or so in a couple weeks, and I'm going to probably pick a book or two to read over that break. Thinking about that, I realized that at a practical level, I have so many books to choose from that I probably will not read all of them straight through any time soon (if I'm honest with myself, maybe even ever). So it'll be a tough decision. I'm probably going to spend at least half an hour going through my long series of unread books and deciding which category of philosophy to even read from (if I can get myself to the point of deciding to read philosophy instead of something else). Then, supposing I've chosen a category (say, ethics), I'm going to have to decide which of several monographs within that category to choose.
One might think that when I'm choosing which book of ethics to read there must be something which marks one of the books off as more worth reading than the others. But I don't think so; I'm probably just going to have to pick one among equally reasonable options. Assuming the authors I'm considering are all equal on obviously measurable standards such as clarity in writing, intelligence, standards of rigor, etc., what other criteria of goodness would there be here? Quality of subject matter? How can I weigh that? If not that, what else? And even if I were to grant that I do a straightforward weighing along a single or several variables, this suggestion seems much less plausible when I'm making the higher-order choice of which philosophical area to read in (or the choice whether to read philosophy at all!).
You might then think that instead of saying my choice was among incommensurables I had multiple choices with an equal degree of goodness along all the variables of goodness, and my choice was arbitrary. In other words, the choices are commensurable, but they just happen to all be equal on the scale of goodness. But as I mentioned above, the subject matter of the books for instance does seem to play into my decision (at least in my case; I don't know about everyone else), and yet this doesn't seem like something I can literally weigh against the alternatives. Probably other incommensurable considerations play into my decision too.
(Note: Making a choice based on considerations and choosing one among alternatives doesn't by itself imply that the alternatives are commensurable. In fact, even if one choice is more rational than another, that doesn't imply the goods chosen are commensurable with those forgone qua goods. There might be some other considerations, for instance purely about what's constitutive of rationality, that bears on what is to be done.)
Maybe this is a case of incommensurability even within a particular category of basic good (viz. knowledge). I wonder how a utilitarian picture of everyday deliberation of this sort would go. And thinking about my own experience, I wonder whether a utilitarian could give a plausible model of such experience.
Okay, that's enough of that. Back to work.