The study is devoted to the analysis of creativity by Petr Mikhailovich Bitsilli, a historian who worked both in Russia and abroad, on the study of religion. The notion of "mentality" refers us to the traditions of the "new historical science" that arose in France in the late 1920s. However, it seems that long before this an anthropologically oriented tradition had developed in Russia. Within its framework there are studies revealing various aspects of the history of the Western European Middle Ages, but this tradition had dedicated itself especially to the individual and ultimately to his culture, way of life, customs, beliefs and so forth-what is customarily called everyday life. These works do not aim to directly study religious experience, religiosity, religion as such, but they prove to be invaluable to the researcher of religion precisely because of his "impartiality" with regard to religious subjects. In this context we can conditionally distinguish two main directions of the research work of Bitsilli. The first is the place of religion in the conditions of change of historical epochs, and the second being religiosity as a cultural and historical phenomenon. It is important to note here that research related to religious issues refers to the early period of his scientific activity. He developed an image of a medieval man from several elements, singling out and characterizing, at the same time, a much larger number of constituents of his mentality. The sources used by the researchers are similar. They were the lives of saints, literary monuments of the era, the writings of mystics and theologians, "visions" the protocols of inquisition. Bitsilli studied the writings of many prominent theologians and philosophers of the era. Relying on the texts of medieval chronicles, in particular, on the literary heritage of Salimbene, Petr Bitsilli reconstructed the religious consciousness of a medieval man.