In 1856 Bogoslav Šulek published a treatise Serbs and Croats, in which he argued against the linguistic definition of Serbian identity by Vuk Karadžić. Šulek’s article had often been cited during later polemics between Serbs and Croats, because its author identifies some of their fundamental causes. At the same the text could be understood as a sort of manifesto of Croatian-Serbian mutuality and Yugoslav solidarity written from the perspective of a Slovak naturalized in the Croatian milieu. The author of the paper namely concentrates on these two aspects of the text, since he analyzes Šulek’s attitudes presented in the polemic against Karadžić through the prism of the recurrent patterns of Croatian-Serbian controversies and Croatian Yugoslavism of the 19th century.