Defending the New Natural Law's Incommensurability Thesis

New Natural Law (NNL) usually gets a bad rap from certain Thomists due to its embracing the "incommensurability thesis." I'll first explain the basic outline of NNL. I'll then explain the incommensurability thesis, and present an argument for it that I find quite convincing. Finally, I'll defend incommensurability from a common objection, and actually show how the objection favors incommensurability. Hopefully my defense will help illustrate the intuitiveness of the thesis.

First, a little explanation of NNL. NNL derives specific moral/practical norms by positing two things:

• (1) A set of basic goods--things that are intrinsically good/valuable/worthwhile for humans to pursue. So, they are always "worthy of pursuit." In other words, they are always "to-be-pursued." Also, the basic goods can make immediately intelligible one's action, and are thus reasons for action. This is very important: The basic goods are the fundamental reasons for action; the fundamental "building blocks" of practical rationality. Examples include knowledge, life, friendship, aesthetic experience, and excellence in play.
  
  Let's consider an example. For instance, suppose you ask me, "Why are you running?" and I say, "To help my heart get stronger," to which you reply, "Why do you want to make your heart stronger?" If my answer is, "For the sake of my health, that I might live and live to the full," then this is a "question-stopper;" you can immediately see why I might want to do this, and thus health is a reason for acting that makes my action immediately intelligible; it immediately "make sense." This is because acting for the sake of someone's health is intrinsically valuable and worth doing.
  
  This is the first part of NNL: There is a set of basic goods, as defined above.
• (2) A set of principles of practical reasonableness--these are principles or rules that tell us how it is reasonable to respond to instances of the basic goods. Examples include the golden rule, the prohibition against directly intending to harm a basic good for the sake of something else, rules against arbitrarily discriminating against the goods of certain people, the rule of being reasonably efficient in how one pursues one's plans, etc.

So, we start out with a list of things that are intrinsically good for us to pursue, and then there are rules that tell us how it is reasonable for us to go about pursuing them. The list of goods, in conjunction with the rules for practical reasonableness, ultimately tell us what actions are permissible as well as what actions are obligatory. They tell us what we may permissibly do, as well as what we ought to do. These rules are taken to be constitutive of practical reasonableness; they are supposed to follow from the very nature of practical rationality.

Much more needs to be said here obviously. Many books have been written. However, I don't need to get too much into the details of this for the sake of my post here. That's just the basic idea.

Now, one of the ideas about the basic goods that motivates some of the principles of practical reasonableness is the incommensurability thesis. Here is the thesis of incommensurability:

• (INC) For each basic good x, it is not the case that x offers all the goodness ("to-be-pursuedness") of some other basic good and more.

See, for instance, Christopher Tollefsen's helpful paper. NNL theorists use the incommensurability thesis to present what I think is one of the strongest arguments against consequentialism of any sort.

Now, the motivation for the incommensurability thesis, as I've stated it, is that it seems that each good is beneficial to humans in a way which none of the other goods is. It has a unique type of goodness. Health is good for us in a way that knowledge is not, which is good for us in a way that friendship is not, and so on. If on the other hand we supposed the contrary of incommensurability, then some basic good x would offer all the goodness and more of some other basic good, say y. But then it's hard to see how y could make one's action immediately intelligible (which is part of the definition of a basic good). After all, if someone says, "I did this action for the sake of y," then in some circumstances you can reasonably say, "Well, you should have acted for the sake of x instead, since it offers all the goodness and more of y. So why didn't you?" In which case y would not be a basic good, since acting for the sake of y should make one's action immediately intelligible, and in this case it doesn't. But that's a contradiction, since we assumed y is a basic good. So the incommensurability thesis is true.

Now, one objection is that it seems we should be able to prioritize the goods. Religion is more important than life, life is more important than knowledge, knowledge is more important than fun, and so on. This seems plausible to some. But, if NNL is right, none of these can be "weighed" against the others, since none of them offers all the goodness of any of the others and more. So, the objection goes, if incommensurability holds, then we can't prioritize the goods.

Libraries: A Case of Practical Incommensurability

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.