Poland was a tolerant country during the 15th and 16th centuries and it was only during the reigns of Zygmunt III Waza (Sigismund III Vasa) and Władysław IV – after the introduction of the Jesuit Order – that dissenters (Protestants) began to be persecuted. Poznań and Leszno were important centres of dissent in Wielkopolska.
Religious dissenters, exiles, and people bereft of prospects and fearful for their lives started pouring into Poland during the counterreformation. An especially large number came from Bohemia. John Amos Comenius (Czech: Jan Amos Komenský, Polish: Jan Amos Komeński) – teacher, philosopher, poet, Unity of the Brethren member, and University of Heidelberg alumnus, was among them. Deprived of all means of earning a living in his homeland, he settled in Leszno in 1625, with Rafał Leszczyński’s consent. The city soon became a Unity of the Brethren stronghold. Comenius took up a teaching position before becoming rector of the local secondary school, where he devoted himself to study. His physics and astronomy textbooks were penned here during this time, as was his enormously popular Latin textbook Ianua Linguarum Reservata. This is also where Comenius wrote his greatest pedagogical work, Didactica Magna, in which he advocated teaching beginners in their native language and only introducing Latin lessons at the second level. Comenius was a prolific writer of poetry and school plays and translated a lot of verse into Polish. He also devised a philosophical theory that proposed restructuring the world in a common spirit of peace, equality and freedom.