 Advocates of negative conceptions of freedom typically restrict the range of obstacles that count as constraints on freedom to those that are brought about by other agents. For theorists who conceive of constraints on freedom in this way, I am unfree only to the extent that other people prevent me from doing certain things. If I am incapacitated by natural causes — by a genetic handicap, say, or by a virus or by certain climatic conditions — I may be rendered unable to do certain things, but I am not, for that reason, rendered unfree to do them. Thus, if you lock me in my house, I shall be both unable and unfree to leave. But if I am unable to leave because I suffer from a debilitating illness or because a snow drift has blocked my exit, I am nevertheless not unfree, to leave. The reason such theorists give, for restricting the set of relevant preventing conditions in this way, is that they see unfreedom as a social relation — a relation between persons (see Oppenheim 1961; Miller 1983; Steiner 1983; Kristjánsson 1996; Kramer 2003; Morriss 2012; Shnayderman 2013; Schmidt 2016). Unfreedom as mere inability is thought by such authors to be more the concern of engineers and medics than of political and social philosophers. (If I suffer from a natural or self-inflicted inability to do something, should we to say that I remain free to do it, or should we say that the inability removes my freedom to do it while nevertheless not implying that I am unfree to do it? In the latter case, we shall be endorsing a ‘trivalent’ conception, according to which there are some things that a person is neither free nor unfree to do. Kramer 2003 endorses a trivalent conception according to which freedom is identified with ability and unfreedom is the prevention (by others) of outcomes that the agent would otherwise be able to bring about.)