Most contemporary scholarship affirms that the Christian and Islamic medieval political imperative was about the preservation of order and stability. We considered this characterization insufficient, given the treatment of the concept of religious and political justice by medieval thinkers in both traditions. In fact, Christian and Islamic political theologies stress that the rulers of their respective communities should 'mirror' divine justice. They also emphasize the need to obey the ruler for the sake of preserving order in their societies. The present study then argues that there is an inconsistency between the emphases on political obedience on the one hand, and the religious imperative of political justice on the other. As a result, Islamic and Christian thought is permeated with a certain degree of anxiety that made more than one Muslim or Christian author uncomfortable. This dissertation is a study of such anxiety. We first survey the influence of Greek and Persian philosophical heritage, centered in harmony and stability for both traditions, as found in the Eastern political concept of the "Circle of Justice". Second, we contrast this influence with the religious meaning of justice as religious righteousness, a theological imperative found in both traditions, and represented in Islam under the maxim of "commanding good and forbidding evil". To do so, we focus on Christian and Islamic Mirrors for Princes up to the 16th century, a literary genre known as part of the political and theological discourse in both traditions. The major contribution of this study is to show the commonalities in Christian and Islamic political theology, particularly in their treatment of the key religious and political values of justice and obedience.