Boltanski, L. and L. Thévenot (2006 [1991]) On justification: Economies of worth. Princeton: Princeton University Press.
To best explain what B & T’s book is about, please allow me a moment to relate a brief representative anecdote, which ought to facilitate the explanation. I don’t have a car, and I haven’t for years. I have a drivers license, and I can drive. I just don’t own a car, and I haven’t owned on for a decade. Not owning a car for a decade has afforded me a privilege insight into car culture. Not driving is difficult—in America at least. The reasons why are manifold. For one, the entire country was designed around the automobile. The west coast is particularly bad. So, in L.A., for example, it’s pretty much impossible to get around without owning a car, since the city itself is so spread out, and the public transportation system isn’t that great. At the level of infrastructure, then, not owning a car is difficult in America. The infrastructure of America itself persuades you to own a car. However, owning a car also encouraged at the level of taxation. Purchasing a car is something you can subsidize. There are literally financial incentives to owning a car. The government subtly pressures you into owning one through subsidizes and write offs—or so I imagine. While I’m sure I could go on to list other reasons why people are pressured into purchasing automobiles (like how they're status symbols), the reason I want to focus on is the fact that owning a car is a good in itself. People buy cars because, say, it's good for the economy. It's downright American. What this means is, even if you have literally no reason for owning a car whatsoever, like I do, since I live right next to where I work, there is still a normative pressure to purchase a car. For example, I've heard rejoinders like, "Don't you want to be independent?" I don't really care to. I don't mind hitching a ride with a friend for that one time a month when I need to get across town--or, I just take the bus. Again, I could go on to tell you interesting stories about people's reactions to my not owning a car, but I've given you just enough context to understand what B & T's book is about. B & T's book is about one particular type of persuasion, how people are persuaded by situations to justify their actions by appealing to higher levels of generality (i.e., the common good).
But why the metaphor? The metaphor is important because it clues us into an important aspect of this book, namely, what's new and exciting about it. On Justification is a work of sociology. Up until the point at which this book was published in France, which was in 1986, I think, sociology was governed by this guy Pierre Bourdieu. All French sociology was either explicitly or implicitly Bourdieuian. Bourdieu was particularly known for this idea of habitus, which states that you are subtly determined by where you come from. I can't put it any better than this:
In this kind of sociology, at least in the way it is seen by Boltanski (and I tend to share his view), the sociologist knows more about the actors than the actors themselves. Indeed when the actors think they behave on the basis of authentic desires, preferences, evaluations, the sociologist can always trace those mental states back to some habitus formation, to unconscious strategies, and ultimately to the structures of the field. For instance, I am quite sure that I like Beethoven because his music is very powerful, lying somewhere between the classical harmonies of Mozart and Haydn and the sometimes tiring excesses of romanticism. But in reality I like Beethoven because I am driven by my desire for distinction which tells me that, in the “petit bourgeois” academic world where I live, liking Beethoven is a necessity to be valuable. I just try unconsciously to follow the rules of the field. But as my semiproletarian habitus did not prepare me to naturally appreciate Beethoven, I cannot feel that the metallic sound of Herbert von Karajan – that was much favoured when I was young – Is now desperately out of fashion. (Jacquemain 1)
Importantly, for Bourdieu, the habitus is located, fixed.
To understand this better, we might ask for Bourdieu to explain why people are inclined to purchase a certain kind of car. He might say that people buy nice cars because they are either trying to reproduce a certain lifestyle or rather that they are trying to move up in the society's class structure. It's important to understand that Bourdieu's schema has great predictive power. For him, class power explains institutions. That is, something like class is necessary in order to explain why people would make super counterintuitive decisions--like buying a car you can't afford, or buying cars you don't need, etc. Either way, for Bourdieu, class is located. You can point to it. If you come from money, you can't escape the influence that the upbringing has on you.
My point of turning to the metaphor is to underscore the idea that certain economies of persuasion don't have a fixed. locus. In a way, it's like Bourdieu is saying, if you completely redesigned a city, or if you redesigned a city around walking instead of driving, then people would stop driving, since you've eliminated the source of people's desire to drive (i.e., the infrastructure). However, people's motivations are much more complicated than that. As I was saying earlier, people's motivation to drive is tied not only to infrastructure or even culture, but also conceptions of the common good. And I think that last part is really key: culture influences decisions, certainly. In our culture, for instance, it's important for men to be seen as independent, as providers, and even as mobile. That culture exerts a pressure on men to purchase cars. But, similar to what we just saw with infrastructure, if you change the culture, that's not necessarily to say that people will stop buying cars--partly because of infrastructure, sure, but also because of how cars are imbricated in our conception of the common good. To stop buying cars would be bad, say, because of how tightly dependent the American economy is dependent on the automobile industry--gas station employees, factory workers, etc.
What's at stake, though, isn't between culture and morals, I don't think, but rather between culture and certain ideas about what counts as just. For one, the latter are much older than the former. The latter have a long history, whereas the former are epoch specific.
Either way, what is On Justification about? It's about a certain class of political ideas that are themselves persuasive, regardless of whatever content they're used to justify. Or rather, to be more precise, it's about a certain class of thought. When I was a study of Cathy Chaput, she'd lecture about the movement of idea to thought. So, for example, Friedrich Hayek came up with a bunch of ideas, then those ideas slowly reified into common sense (i.e., neoliberal doctrine). There's therefore a difference between certain political ideas and ideas that themselves have histories and have started to mediate entire ways of life.

