Abilities are powers an agent has to perform various actions. They include common abilities, like walking, and rare abilities, like performing a double backflip. Abilities are intelligent powers: they are guided by the person's intention and executing them successfully results in an action, which is not true for all types of powers. They are closely related to but not identical with various other concepts, such as disposition, know-how, aptitude, talent, potential, and skill.
Theories of ability aim to articulate the nature of abilities. Traditionally, the conditional analysis has been the most popular approach. According to it, having an ability means one would perform the action in question if one tried to do so. On this view, Michael Phelps has the ability to swim 200 meters in under 2 minutes because he would do so if he tried to. This approach has been criticized in various ways. Some counterexamples involve cases in which the agent is physically able to do something but unable to try, due to a strong aversion. In order to avoid these and other counterexamples, various alternative approaches have been suggested. Modal theories of ability, for example, focus on what is possible for the agent to do. Other suggestions include defining abilities in terms of dispositions and potentials.
An important distinction among abilities is between general abilities and specific abilities. General abilities are abilities possessed by an agent independent of their situation while specific abilities concern what an agent can do in a specific situation. So while an expert piano player always has the general ability to play various piano pieces, they lack the corresponding specific ability in a situation where no piano is present. Another distinction concerns the question of whether successfully performing an action by accident counts as having the corresponding ability. In this sense, an amateur hacker may have the effective ability to hack his boss's email account, because they may be lucky and guess the password correctly, but not the corresponding transparent ability, since they are unable to reliably do so.
The concept of abilities and how they are to be understood is relevant for various related fields. Free will, for example, is often understood as the ability to do otherwise. The debate between compatibilism and incompatibilism concerns the question whether this ability can exist in a world governed by deterministic laws of nature. Autonomy is a closely related concept, which can be defined as the ability of individual or collective agents to govern themselves. Whether an agent has the ability to perform a certain action is important for whether they have a moral obligation to perform this action. If they possess it, they may be morally responsible for performing it or for failing to do so. Like in the free will debate, it is also relevant whether they had the ability to do otherwise. A prominent theory of concepts and concept possession understands these terms in relation to abilities. According to it, it is required that the agent possess both the ability to discriminate between positive and negative cases and the ability to draw inferences to related concepts.