 Political science studies the tasks of the politician or statesman (politikos), in much the way that medical science concerns the work of the physician (see Politics IV.1). It is, in fact, the body of knowledge that such practitioners, if truly expert, will also wield in pursuing their tasks. The most important task for the politician is, in the role of lawgiver (nomothetês), to frame the appropriate constitution for the city-state. This involves enduring laws, customs, and institutions (including a system of moral education) for the citizens. Once the constitution is in place, the politician needs to take the appropriate measures to maintain it, to introduce reforms when he finds them necessary, and to prevent developments which might subvert the political system. This is the province of legislative science, which Aristotle regards as more important than politics as exercised in everyday political activity such as the passing of decrees (see EN VI.8).