Mikołaj Sienicki

A Protestant, near the end of his life he became a member of the Polish Brethren and one of the major initiators of, and contributors to the Warsaw Confederation, which introduced new laws of religious tolerance in the Polish–Lithuanian Commonwealth, on a scale unimaginable in contemporary Europe.

Soon afterward, he took an active interest in politics, joining his father in the sessions of the local parliament (sejmik) of his home region (Chełm land or ziemia chełmska).

[2] From 1553 onwards, he was an active member of the executionist movement, a political party of the middle nobility that opposed the magnates and sought to reform the kingdom.

A vocal supporter of religious tolerance and the need for national unity, he strongly criticized the delaying tactics of the Catholic clergy, which threatened the political stability of the newly founded Commonwealth during the uneasy time of the interregnum.

After the confederation had been signed, he was one of the major supporters (together with other pro-reform-minded Polish politicians like kanclerz Jan Zamoyski) of the inclusion of its provisions in the Henrician articles and later in the pacta conventa.