Final answer:
Aristotle referred to politics as the 'master-science' because it incorporates other sciences in pursuit of the highest good, which is a virtuous life in a well-governed society.
Step-by-step explanation:
Aristotle, one of the most influential philosophers of all times, considered politics as the 'master-science' because it makes use of other sciences and fields of study. This was due to the fact that political science aims at the highest good and, in a way, it orchestrates the application and utility of the other sciences. Aristotle's work spanned various domains such as metaphysics, ethics, natural philosophy, and more, hence establishing a comprehensive system of understanding the world.
In Aristotle's hierarchy of sciences, practical sciences like ethics and politics were held in higher regard because they dealt with human behavior and the governance of people. The good life, according to Aristotle, is one lived in accordance with virtue, and the study of politics is essential in understanding how to cultivate and maintain a society that allows its citizens to live such a life. Thus, political science serves as the master art that utilizes the understanding attained from other sciences to guide human actions towards their ultimate end.