In 1973, he received the Herder's Prize in Vienna. The summer of that year he spent together with Magdalena and Zbigniew Czajkowscy in Greece. He came back to Poland in autumn 1973. He spent the academic year of 1973/74 giving lectures at the University of Gdansk. In 1974, he wrote the 'Letter of 15' ('List 15') which was about the laws of the Polish Community in the Soviet Union. In December 1975, he signed 'Letter of 59' ('Memoriał 59') against the changes in the Constitution of the People's Republic of Poland forced by the communist party introducing mostly declarations of eternal loyalty of Poland to the Soviet Union. In 1974, he settled at Promenade's Street in Warsaw.