Political science is the study of the origins, organization, and sphere of activities of the state. Political scientists study all aspects of government. They are concerned with the problem of how authority is derived and how it is exercised. They investigate the political behavior of officials and voters and try to analyze the factors that affect the formation of public policy. Some political scientists specialize in political philosophy, or theory, and others specialize in comparative government, or the study of the differing political systems of various states. Some are concerned mainly with international relations, and others are interested chiefly in public administration or in municipal and local government. All make use of research in the other social sciences, history, economics, philosophy, sociology, and psychology.
Political scientists sometimes distinguish three main approaches to political thought. From early times some societies have considered the state an instrument having divine authority to carry out God's law, and political thought has been closely related to religious thought. Examples are ancient Egypt, the medieval Islamic Empire, and Geneva during the Reformation. In many societies, government has been the subject of moral philosophy and political analysis. For example, Plato and Aristotle in ancient Greece thought that the state was the institution through which man could achieve his highest development. They classified various kinds of government, and each outlined what he considered to be the best kind. The great classic writings on political science, such as the works of Thomas Hobbes, John Locke, Jean Jacques Rousseau, and Baron de Montesquieu, were largely analytical and philosophical. They dealt with such ideals as liberty, justice, and equality and with such practical matters as voting, legislative organization, executive responsibility, and the protection of property.
In Renaissance Italy the diplomat Niccolo Machiavelli was the first political scientist to record in detail the actual methods employed in getting and keeping political power. In his society these means were mainly fraud, corruption, and ruthless force. Since that time, political scientists have continued to stress an analytical approach to their work. They employ observation and comparison, refined statistical analysis, and sometimes even mathematical game theory in attempting to make predictions about political results.