The _Defensor Pacis_ is a treatise on politics written by Marsilius, or Marsiglio, a canon of the church of Padua, in 1324. His authority is the _Politics_ of Aristotle, which Marsilius knew from a Latin summary current in the Middle Age. From this as a basis he constructs a political theory and tests the existing institutions by it. The work is divided into three parts; the first two form a diffuse essay, and the last is a summary of his arguments in the form of forty-two _conclusiones_, which are translated here, because they give in a concise form the essential points of his theory. As regards the political situation of his own time, the general tendency of the treatise is imperial and anti-papal; it was used by Ludwig IV [the Bavarian] in his conflict with the Avignon popes. Hence it was regarded by the papal party as unorthodox and heretical. In the bull of John XXII, 1327, five statements were selected and condemned as heresies (see no. 166). His views on the origin and nature of the state are Aristotelian: the state is a perfected community existing for the good of the people; the supreme power resides in the body of the citizens, who make the laws, and choose the form of government, etc. The prince rules by the authority of the whole body of citizens. To this body Marsilius gives the name _legislator_. The elective monarchy is the form of government preferred by Marsilius, whose ideal state thus corresponds in theory with the holy Roman empire. His views on the relation of the state and the church are very different from the views common in the Middle Age. The supreme institution is the state which has established the priesthood or the church to look after the spiritual welfare of its citizens. Hence the state has the right to control the church, but the church has not the corresponding right to control the state. The treatment of the church in itself is also interesting. Marsilius attacks the Petrine theory and the whole papal structure. All bishops are equal in religious authority, deriving their power immediately from Christ. If one priest or bishop is placed over another it is for the purpose of organization, and the authority of the superior is derived from the state. He also asserts that within the church the supreme authority is not the pope, but the general council of Christians. Conclusion 1. The one divine canonical Scripture, the conclusions that necessarily follow from it, and the interpretation placed upon it by the common consent of Christians, are true, and belief in them is necessary to the salvation of those to whom they are made known. 2. The general council of Christians or its majority alone has the authority to define doubtful passages of the divine law, and to determine those that are to be regarded as articles of the Christian faith, belief in which is essential to salvation; and no partial council or single person of any position has the authority to decide these questions.