 His last book, "Nirvana" (1928), deals with his understanding of philosophy as correlated with poetry, with philosophy's influence on his outlook and its being a source of inspiration for him.The work revisited themes found in the earlier "Evanghelia naturii".A sympathizer of the National Liberal Party, with leading member Vintilă Brătianu a backer of his theories, Zeletin nevertheless joined the People's Party.