Comparative studies do not deal with objects, but with relations. Relations do not exist, they have to be established. On the basis of the four elementary forms of relation – unity, separation, dialogue and determination – there have been distinguished four basic forms of comparative studies. Semantic comparison is immanent to the literary system and mutual; functional comparison is also mutual but goes beyond the literary system; cultural transfer goes beyond the literary system but is unilateral; and literary influence is unilateral but immanent to the literary system. Two of these relations examine cultural or literary systems immanently – one traces the wandering of tropes and motives, the other reconstructs cultural interrelations. The other two forms of comparative studies go beyond literary and cultural systems, one in the direction of the social functions of literature, the other in the direction of facts and objects. The unilateral relations are based on succession in time, while the mutual forms imply simultaneity – either they are contrasted to one another with respect to their function, or they are put into a typological equivalence. Against this background, the article discusses Wacław Borowy’s description of different forms of comparative literature. While Borowy distinguishes “valid” and “invalid” forms of comparative studies, this article tries to demonstrate their equal epistemological value and to systematically arrange the different answers which can be expected from them.