Solidarity is a significant but poorly understood feature of political life. It is typically conceived, in “associative and teleological” terms, as working together for common political aims. But this conception misses the fact that solidarity requires individuals to will collective ends despite incompletely shared interests. Careful consideration of these elements reveals four “dynamics of solidarity”: its characteristic duties, the durability of commitments made in solidarity, the deference it involves, and its effects over time on agents’ habits and capacities. In this (...) article I describe these dynamics, first contrasting solidarity-given duties with duties of beneficence, justice, and loyalty. These contrasts lay bare the distinctive durability of solidarity, which differs from both the liberal’s commitment to justice and the loyalist’s commitment to the group. I then discuss deference, a feature of solidarity that has implications for individual engagement in political life more generally. Finally, I discuss the effects of solidarity on agents’ intellectual and physical capacities. I conclude by drawing out implications of these dynamics, challenging Tommie Shelby’s influential conception and justification of black solidarity and buttressing Philip Soper’s rejection of the Principle of Autonomy. (shrink)