What, exactly, is solidarity? And how does it differ from another term that Kymlicka (2015), uses in his article, namely an ethic of “social membership”? Kymlicka (2015), notes the virtual absence of theorizing on ‘solidarity’ outside of sociology. Indeed, even within sociology, Kymlicka cites social theorist Jeffrey Alexander to argue that solidarity has “disappeared” as a concept and topic. Why then use this term? Kymlicka does not elaborate, beyond a hint that, empirically, contemporary societies function based on a sense of community that goes beyond the coercion of laws or formal institutions and, more explicitly, that a theory of equality that includes economic justice can find the necessary “glue” for a robust welfare state through national solidarity. My own instinct is to feel uneasy about solidarity, and more comfortable with a language of membership. This reaction stems, I think, from concerns about the strength and primacy of collective obligations inherent in each term, and the openness to multiple and even cross-cutting obligations. According to the Oxford English Dictionary, solidarity is “The fact or quality, on the part of communities, etc., of being perfectly united or at one in some respect, esp. in interests, sympathies, or aspirations.”2 Synonyms offered by other dictionaries include unanimity, unity, harmony, cohesion and like-mindedness.3 All of these terms are in tension with Kymlicka’s (2015), starting point: the centrality of democracy and, as he puts it, “facts of pluralism.” It also sits awkwardly, I feel, with a key precept of multiculturalism, namely the recognition, valorization and support of diversity. In contrast, membership refers to being a “constituent element within a social or other organized structure.”4 The individual is part of a whole, but this does not entail a ‘perfect unity’ requirement. At the same time, the notion of membership is more than just a transactional or instrumental relationship, like two parties agreeing to a contract. As part of a social group, relationships are implied to extend over some time period, which can generate norms around rules, reciprocity and even engagement in a common enterprise agreed to by members. It is, in a sense, a thinner version of collective action than solidarity, and does not carry the same baggage of like-mindedness.