This article is concerned with the scholarly historical works of Ján Kollár (1793–1852), primarily his Dobré wlastnosti Národu Slowanského (The Good Qualities of the Slav Nation, 1822). In the introduction, the author distinguishes between Romantic historicism and Comtean positivist historicism. The application of the positivist conception resulted, on the one hand, in the marginalization of Kollár’s works with historical subject matter, but, on the other hand, an important part of his thinking made its way into the modern national culture and national consciousness. The author, in the first part of the article, considers the broader historical context of Dobré wlastnosti Národu Slowanského. Following on from previous research, he reveals the influence of Herder, particularly, however, he points to the Hungarian sources from which, he argues, Kollár was inspired in his definition of the ‘good qualities of the Slav nation’. The author then compares in detail the article ‘A régi Magyaroknak Vallásbéli s Erkölcsi Állapottyokról’ (The Religious and Moral Stages of the Ancient Hungarians), by the Veszprém canon Johann Baptiste Horvath (János Horváth, 1732–1799), published in Tudományos Gyüjtemény (Scholarly Miscellany), and demonstrates the extent to which Kollár drew on it and suggests why Kollár concealed his original source.