During this period, Przywara held hundreds of lectures all over central Europe, most famously at the Davos seminar in 1928 and 1929. He was also extremely prolific, authoring between 1922 and 1932 as many as 17 books and 230 articles and reviews (and eventually over 40 books and 800 articles and reviews). During this time he also engaged in ecumenical dialogue with the Protestant theologian Karl Barth, who considered Przywara to be his most serious opponent, indeed "the giant Goliath incarnate," inviting Przywara to his seminars in 1929 (in Münster) and 1931 (in Bonn).