In classical political thought, the concept of a tyrant is used (simplified) to refer to an autocrat who has betrayed his monarchical mission to manage the state and lead it towards the common good. Contrary to this mission, however, the tyrant oppresses the state’s residents and asserts his personal desires contrary to the general good, using violence whether brutal or less cruel. However, the defining feature of tyranny is not violence, which is legitimate in the interest of the public in every form of government, but rather the focus on purely personal gain at the expense of the general welfare, and the use of violence precisely for personal gain. (Of course, it should be noted that, in ancient times, the term ‘tyrant’ was not always perceived negatively, either theoretically or practically.)
Therefore, a tyrant is not a monarch who suppresses a bloody and decaying revolution by equally bloody means to preserve the communal good; rather, it is a ruler who uses similar means to satisfy their own selfish desires and gain personal profit at the expense of the general welfare. Similarly, according to this definition, a representative of a secular totalitarian regime based on a particular ideology should not be called a tyrant. He does not have to act for his own personal gain, and he may, of course, have the impression that he is working for the common good since he is an unbeliever. His removal usually has no effect because the secular ideology of gratitude to its metaphysical background endures, even after the death of the leading official.
For a Christian, an anti-Christian secular regime (or any anti-Christian mode) is basically a tyrannical system. In this case, the classic division into monarchy, aristocracy, and politea loses its meaning, because it is irrelevant whether Christians will be persecuted by an autocrat, an elite, or elected people’s representatives. The problem lies outside the political system. For a Christian, any form of suppression of Christianity is automatically tyrannical.
All scholastic thinkers assume a political situation within the Christian state. A monarch who strives to suppress Christianity or harm the natural good of the Christian state is seen as a tyrant who has abused his position. However, a global non-Christian or anti-Christian regime or state (e.g. Islamic or pagan) is generally perceived as unacceptable. Essentially, their vision of the state can be described as a dichotomy: Christian states versus missionary states (non-Christian states that consciously or unconsciously prevent people from knowing the Gospel).
This vision of reality is found in St. Augustine’s concept of two states: the spiritual and the secular. Whether they want to or not, all orthodox Christian concepts of politics must appeal to St. Augustine, unless they serve some modern-day ideology. The notion of a pluralistic, multi-religious state would have seemed absurd to the scholastics. The political conceptions of St Thomas Aquinas and John of Salisbury are only feasible within a Christian state that participates in Civitas Dei.
Whether an individual in a Christian state or a general in an anti-Christian state, tyranny is undoubtedly perceived as evil. Christian thinkers have questioned how Christians should respond to this evil. A fundamental problem for Christians is whether a tyrant can be removed by force, i.e., by killing them, either collectively or individually. Some Christian thinkers rejected such a practice (Tertullian and Lactations), while others did not exclude it (St. Augustine), but neither group dealt with the issue in much detail.
John of Salisbury (1115–1180)