This article presents the basic achievements of the psychology of religion in the Lvov-Warsaw School of K. Twardowski, their developments and significance for the contemporary psychology of religion. Twardowski’s School existed parallel to other European psychological schools: the Würzburg School, founded by Oswald Külpe, and the Dorpat School of the Psychology of Religion, founded by Karl Girgensohn. The article presents two research trends in the psychology of religion resulting from Twardowski’s works, specifically research on mental acts and religious beliefs with (...) use of introspection and research in the field of cultural-historical psychology. The theory of acts and products, and the theory of cratism/power played crucial roles here. Psychological investigations into religious beliefs were also dominated by the psychological principle of contradiction, and the obtained results also seem to be important today. (shrink)