According to Aristotle, virtue primarily involves rationality and the use of a person's rationality. Rationality and happiness are activities of the soul, and virtue is the excellence of these activities.
Humans are the only life forms that have a soul, the source of rationality.
Thus, humans have a duty to always use their intellect. Emotions are things humans feel, like anguish or happiness that are followed by pain or pleasure. Capacities are a person s ability or capacity to experience or express something. Since people are not considered good or bad based on their emotions, virtue cannot be an emotion. Virtue is not a capacity either, because virtue involves choice, not abilities.