When natural inability removes freedom without another agent being the cause, the person falls into a third category — neither free nor unfree.

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 a