The Jesuits were brought to Poland in 1564, mainly to establish schools. They soon established an academy in Vilnius, and then opened colleges in Braniewo, Pułtusk, Poznań, Lublin, Jarosław, Nieświeże and Lwów, to which young men from various parts of the Commonwealth flocked. In the Jesuit schools, tuition was free, but the teachers lived on the income from the estates. Almost all Jesuit college foundations were based on land, i.e. manor houses. Not only were the Jesuits concerned with the fair and humane treatment of their subjects on the estates, but from the beginning they tried to give them special spiritual care. Priests and seminarians devoted themselves with great enthusiasm to teaching the catechism to the rural population during the Christmas and summer holidays, and especially during the plagues that plagued Polish cities in the 16th and 17th centuries, when schools were closed and moved to the countryside. In this apostolic work among the rural population, the Polish Jesuits did not limit themselves to their own subjects. Many of them stayed on the estates of bishops and nobles, where they not only performed their clerical services among the courtiers, but also kept an eye on the farm workers and the surrounding rural population, for whom they catechised, heard confessions and preached. Through this apostolic work, which was carried out in almost every town and village of the republic, in confessionals and in private conversations, the Jesuits became aware of the great injustice and ruthless exploitation of the Polish people. This led them to defend the peasants in their sermons and writings. Among the preachers, the following Jesuits can be identified Jakub Wujek, Piotr Skarga, Tomasz Młodzianowski, Mateusz Bembus. However, the sermons and writings of the Polish Jesuits, as well as those of Frycz Modrzewski and other political writers, did not lead to a decisive improvement in the lot of the peasants in Poland. Even the oath taken by Jan Kazimierz before the senators in 1656 had no power in this matter. A fair arrangement of economic relations between states could only be achieved by a strong royal power, and this was lacking in Poland under the Jagiellons and the elected kings.