 Abilities, then, are a kind of power. What kind of power, precisely, is an ability? As the term will be understood here, there are two additional conditions that a power must meet in order for it to be an ability. First, abilities are distinguished by their subjects. Abilities are properties of agents, rather than of things that are not agents. Objects have dispositions and affordances — as a glass is disposed to break when struck, or affords the drinking of liquid — but they do not have abilities. Being a power of an agent is not, however, a sufficient condition for being an ability. This is because agents have powers that are not abilities. Therefore, second, abilities need to be distinguished by their objects: abilities relate agents to actions.