This article is devoted to the original sources from which the Latvian art historian Kristaps Eliass (1886--1963) developed his theoretical principles. Eliass wrote biographical and theoretical articles, as well as books about Dutch and French art, and of particular importance to him were the writings of German authors Richard Muther and Julius Meier-Graefe, both of whom were prominent at that time. During the Soviet period, Kristaps Eliass was praised for his texts where he emphasized the influence of social conditions on arts, linking it directly to the progressive role of Karl Marx's conception. However, the work of Muther and Meier-Graefe is much closer to that of Eliass - they saw art history as a systematic and ordered interpretation of processes, criticizing the separation of art and life that was typical of capitalist societies. Kristaps Eliass also placed a high emphasis on the personality of each artist, thus reflecting the ideas of Romanticism, as well as the influential thinking of Arthur Schopenhauer. In his writing Eliass also drew upon the ideas of the historians and theoreticians Alois Riegl and Wilhelm Worringer, among others, about the regularities that are found in the evolution of the arts. He also took advantage of conclusions which the optician Hermann von Helmholtz developed about the impossibility of copying nature directly in a work of art. During the dogmatic period of Stalinism, Eliass' work fell out of favor and was criticized for emphasizing sociological conditions inadequately. Eliass always tried to maintain a certain balance between the importance of the spirit of the times or the class struggle on the one hand, and the value of forms created by a self-expressive artist on the other.