To make their strength felt still more politically, the Protestants, including the Lutherans, the Calvinists, and the Bohemian Brethren, entered into a certain form of union at Sandomir, April 14, 1570, known as _Consensus Sandomiriensis_. By this agreement, while each body retained its organization and form of worship, the three Protestant bodies pledged themselves to preserve peace and harmony among themselves and to act together politically.[179] Due to the political strength of the Protestants, the Polish szlachta entered during the interregnum after the death of Sigismund Augustus into a Pact of Confederation at Warsaw in 1573, by which religious toleration and equality were legally established in the realm, and had to be sworn to by every newly elected king.[180] This marked the climax in the development of the Reformation in Poland. The causes of this remarkable development of the Reformation movement in Poland were not only political, as previous studies have sufficiently established, but also social and economic. To show this is the purpose of the present study. [1] Walerjan Krasiński, Zarys dziejów Reformacji w Polsce, Warsaw, 1903, vol. i, p. 26; Wł. Smoleński. Dzieje narodu polskiego, Warsaw, 1904, p. 21. [2] Smoleński, pp. 30-31; Krasiński, vol. i, pp. 29-30. [3] Krasiński, vol. i, p. 31. [4] Ibid., vol. i, pp. 31-32. [5] Smoleński, pp. 41-42. [6] Krasiński, vol. i, p. 34. [7] Smoleński, p. 31. [8] An interesting and detailed account of this incident is given by Stanislaus Smolka in his Szkice historyczne, Warsaw, 1883, pp. 259-281. See also Eugene Starczewski, Możnowładztwo polskie, Warsaw, 1914, pp. 114-115. [9] Krasiński, vol. i, pp. 34-36. [10] Smoleński, pp. 25-26. [11] Ibid., p. 31; Krasiński, vol. i, p. 30. [12] Smoleński, p. 31; Krasiński, vol. i, p. 37. [13] Starczewski, p. 72. [14] Vincent Zakrzewski, Powstanie i wzrost Ref. w Polsce, Leipzig, 1870, p. 112. When the Roman Inquisition called Uchański to appear before it to give account of himself and to be tried as a heretic, he refused to do so, protesting against being called a heretic before a previous trial (see Zakrzewski, p. 140). [15] Zakrzewski, pp. 179-180. [16] Smoleński, p. 19. [17] Krasiński, vol. i, p. 32. [18] Smoleński, p. 93. [19] T. Grabowski, Literatura luterska, Posen, 1920, p. 13. Many of the Polish bishops were great admirers of Erasmus, and they constituted, says Grabowski, the vanguard of the reformers. [20] See E. H. Lewinski-Corwin, The Political History of Poland, N. Y. 1917, p. 138; Smoleński, pp. 80-81. [21] Lewinski-Corwin, p. 138. [22] Antoni Lorkiewicz, Bunt Gdański Roku 1525, Lemberg, 1881, p. 7.