The study of leadership is characterized by an expanding set of definitions of the term leadership. Some scholars even set out to know leadership by the identification of traits or behaviors of good leaders. However, the scientific study of leadership requires the identification of a causal theory of leadership. The scientific belief in causation as the common epistemology is the necessary link between the various disciplines interested in leadership (e.g., organizational psychology, statistics, education, or management studies), which allows for the interdisciplinary study of leadership.