One's agency is one's independent capability or ability to act on one's will. This ability is affected by the cognitive belief structure which one has formed through one's experiences, and the perceptions held by the society and the individual, of the structures and circumstances of the environment one is in and the position they are born into. Disagreement on the extent of one's agency often causes conflict between parties, e.g. parents and children.
The concept of agency has existed since the Enlightenment. René Descartes' phrase Cogito ergo sum stated that anyone who could think is an agent[dubious ], and any agent capable of knowing that it can think was a subject. Immanuel Kant expanded on this theory by stating that the only way to truly become self-aware is to engage with the outside world. These definitions of agency remained mostly unquestioned until the nineteenth century, when philosophers began arguing that the choices humans make are dictated by forces beyond their control. For example, Karl Marx argued that in modern society, people were controlled by the ideologies of the bourgeoisie, and Friedrich Nietzsche argued that man made choices based on his own selfish desires, or the "Will to Power."
Thinkers have only just begun to empirically explore the factors that cause a person to feel as though they are in control — particularly, in control of a physical action. Social psychologist Daniel Wegner discusses how an "illusion of control" may cause people to take credit for events that they did not cause. These false judgments of agency occur especially under stress, or when the results of the event were ones that the individual desired (also see self serving biases). Janet Metcalfe and her colleagues have identified other possible heuristics, or rules of thumb, that people use to make judgments of agency. These include a "forward model" in which the mind actually compares two signals to judge agency: the feedback from a movement, but also an "efferent copy" — a mental prediction of what that movement feedback should feel like. Top down processing (understanding of a situation, and other possible explanations) can also influence judgments of agency. Furthermore, the relative importance of one heuristic over another seems to change with age.
From an evolutionary perspective, the illusion of agency would be beneficial in allowing social animals to predict the actions of others. If one considers him or herself a conscious agent, then the quality of agency would naturally be intuited upon others. As it is possible to deduce another's intentions, the assumption of agency allows one to extrapolate from those intentions what actions someone else is likely to perform.
Martin Hewson, Associate at the York Centre for International and Security Studies, York University, describes three types of agency: individual, proxy, and collective. Individual agency is when a person acts on his/her own behalf, whereas proxy agency is when an individual acts on behalf of someone else (such as an employer). Collective agency occurs when people act together, such as a social movement. Hewson also identifies three properties of human beings that give rise to agency: intentionality, power, and rationality. Human beings act with intention and are goal oriented. They also have differing amounts of abilities and resources resulting in some having greater agency (power) than others. Finally, human beings use their intellect to guide their actions and predict the consequences of their actions.