Conflicts over the payment of tithes were, therefore, frequent. They occurred as early as the reign of Casimir the Great,[430] and as time went on they grew more bitter and more frequent. Owing to the growth of the church in wealth and of the clergy in arrogance as a result of Wladislaus Jagiello’s great liberality and even subserviency, the nobility was forced to consider measures at the Convocations of Piotrków in 1406 and 1407 for protection against this exploitation.[431] By the Privilege of Czerwieńsk forced from the king in 1422 it further secured itself against the relentless exaction of tithes.[432] A decade later the special privileges concerning tithes given the clergy by Wladislaus Jagiello in 1433,[433] and the king’s assurance that he would assist in the collection of this tax, are evidence of the difficulties encountered. To force the clergy to desist from their pretensions, the nobility, under the leadership of Andrew Zbonsz, Spytek of Melsztyn, and John Strasz, decided at the Convocation of Piotrków, August 15, 1435, to withhold the payment of tithes altogether.[434] A similar resolution was adopted by the Confederation of 1439.[435] These decisions, however, were never fully carried out in practice. In the second half of the fifteenth century, influenced by the economic changes that were taking place and encouraged by such radical humanistic ideas as those of John Ostrorog, embodied in his “Monumentum pro reipublicae ordinatione congestum,” the Polish nobility moved still more resolutely toward the abolition of the tithes.[436] In the sixteenth century this conflict became even more determined. If the nobility objected to the tithes in the preceding century, it did so now all the more. The wealth of the church had increased as a result of the economic changes in progress, the incomes of the clergy were princely, the needs of the country greater and more exacting; and yet the clergy shirked all public burdens and responsibilities. Naturally, therefore, the nobility began to withhold the payments of tithes. The situation was so serious that the clergy became very much concerned. At several of the provincial synods, notably those of 1544 and 1551, they gave a good deal of time to discussions of ways and means by which to force the nobility to pay tithes.[437] But the situation seemed to be beyond repair. Incensed at the immunities, pretensions, and exactions of the clergy, the nobility was turning away in great numbers from the established church to the Reformation after 1550, and thereby was cutting down ecclesiastical revenues.