Steven D. Smith’s The Disenchantment of Secular Discourse is one of the most piercing works in political philosophy I’ve read in a long while. Though it’s brief, by the end of it Smith has turned inside out some of the modern Western world’s most repeated fundamental values, and shown that appeals to them are actually smuggling operations. That is, given the secularizing rules of political conversation, forbidding appeals to metaphysical or religious principles, appeals to those common values (like equality, the no-harm principle, freedom, and others) actually disguise appeals to these larger metaphysical claims. This allows arguers to bring in metaphysics without admitting it, hoping to sway people by associating their controverted positions with values we all profess to accept.
The book is well worth the read. I won’t be doing a full review of the book, but I do want to write a few posts highlighting some of his most useful arguments. The first is about the so-called harm principle. Briefly stated, the idea is that the only justification for interfering with the freedom of people is to prevent harm to other people.
Smith argues that the central problem with the claim’s usefulness is in the definition of “harm”. There are two ways the concept could be defined: subjectively or objectively. When we allow individuals to define when they are harmed in their own subjective experience, we do the former. When we do not take such claims as self-authenticating, but instead measure them against ostensibly objective criteria for what counts as real harm, we do the latter.
Unfortunately for those who want to use the principle as a way to help determine when coercion should be used, neither option can help. In the subjective case, the problem is that such an interpretation of the principle cannot protect liberty in the way its proponents desire. This is illustrated by an example such as the one Smith gives:
Suppose I live in a community in which prudish Victorian types are numerous and wield considerable political influence. The community as a whole thus tends to favor rigorous restrictions on materials that residents regard as pornographic. As it happens, I am a solid citizen with a family and a steady job, but one who happens on occasion to enjoy watching hard-core, XXX films in my living room. I watch these films alone, or sometimes with a few adult friends—academic colleagues, maybe—who have been fully advised about the nature of the materials and have freely chosen to partake. After particularly grueling and inane faculty meetings, perhaps, these ribald festivities help us to loosen up and recover our sanity. But although these viewings are as private as my friends and I can possibly make them (we keep the volume down and make sure to close the curtains), they transgress the community’s antipornography ordinance. So my nosy neighbours (as I regard them) somehow learn of what I am doing, and complain, and the local authorities move to enforce the ordinance against me. … I protest, … I am not harming anyone.
The city council patiently explains, though, … that I am harming other people, in a variety of ways. How? I ask, and the council obliges by explaining two obvious ways in which I am causing harm. … [82-83]
Smith then outlines the two ways in which such behaviour could cause harm. First, “the knowledge that I am watching XXX films in my home causes emotional and psychic distress to my prudish neighbours, who view my practice with abhorrence.”  He notes further that in general we do recognize that emotional distress is a kind of pain or suffering and frustrated preference, and that this principle is enshrined in law.  Second, “what my consenting adult friends and I do in private will surely have some influence over the kind of people we are. … And because we interact with the community—as teachers and lawyers and business people and consumers—it will affect others in the community as well.” 
The obvious conclusion is that if harm is defined subjectively, then the harm principle is not useful for protecting individual liberty over against majority preferences.
It is for this reason, Smith notes, that historic defenders of the principle have surreptitiously or explicitly shifted to an objective definition of harm that evaluates harm claims and determines some are morally relevant and others are not.  The main problem with this gloss is that it ultimately appeals to the kinds of metaphysical principles, or ultimate visions of the good life, that secular political discourse is supposed to rule out as a matter of policy. He shows this in detail with John Stuart Mill and with Joel Feinberg, a contemporary theorist who reasons extensively about the harm principle. [87-93]
Later in the book he deals extensively with Martha Nussbaum, whose political philosophy attempts to provide philosophical foundation for human rights that doesn’t appeal to metaphysics or religion.  Though he does not present it this way, Nussbaum’s philosophy is essentially about the same issue, determining the kinds of harms that are objectively wrong for others to inflict on individuals, since rights are supposed to be things possessed by individuals that make it immoral to behave towards them in certain ways. For this reason, Smith’s points against Nussbaum further reinforce the dialectical pointlessness of the principle.
Nussbaum argues that we can deduce standards for behaviour from observation of human capabilities. More specifically, she says there are ten capabilities that are universal across cultures: life, bodily health, bodily integrity, the use of senses/imagination/thought, emotions, practical reason, affiliation, living with other species, play, and control over one’s environment. 
Smith argues that ultimately Nussbaum’s position has no foundation on its own terms. First, he notes that, on non-metaphysical principles, the mere fact that people are capable of doing things does not mean those capabilities are morally valuable.  Second, when Nussbaum appeals to “intuition” to justify her claims, he notes that not everyone shares her intuitions, historically or in the present.  Third, and related to the previous point, he notes a vicious circularity in her appeals to capabilities:
Nussbaum herself quickly qualifies her initial, more sweeping contention. Noting that “the capacity for cruelty… does not figure on the list,” [of morally valuable capabilities] she explains that “[n]ot all human abilities exert a moral claim, only the ones that have been evaluated as valuable from an ethical standpoint.” Elsewhere she points out that we do not protect capabilities “qua capabilities,” but only upon a “prior evaluation, deciding which [capabilities] are good, and, among the good, which are most central, most clearly involved in defining the minimum conditions for a life with human dignity.” The qualification is offered in passing and in an “of course” tone. Nussbaum seems not to notice that her caveat renders her position circular: it is morally valuable, the amended claim now asserts, to protect and cultivate morally valuable capabilities. …
The circularity effectively negates Nussbaum’s claims that “capabilities” can serve as a source of “philosophical underpinnings” for “universal values.” Instead, capabilities simply become one more item … that stand[s] in need of moral evaluation; they do nothing to supply a criterion or standard of moral evaluation. 
Fourth, Smith notes that Nussbaum has no real response to the argument that her intuitions ought to be supported by argument, except to say that other theorists have the same problem as her. [172-173] This, of course, does not rescue her position, and in fact the metaphysical and religious positions she rejects out of hand could do what she cannot. 
Smith’s arguments are useful in our current social and historical context for some fairly obvious reasons. But I’ll point out just one. If by all accounts the Western world is becoming more polarized, and we want to find a way to bring it back together by talking with each other rather than bludgeoning one another, we have to find a way to talk to each other. We can’t do that if we restrict our conversation to empty words that mask our true motives, and refuse to ever talk about those driving forces.