The article is devoted to the creation of a theoretical model of a subject, undergoing a religious conversion. Contemporary scholars provided in their works extensive bibliographic information and systematized theoretical directions, which are applied now to describe the process of religious conversion. The concept of religious conversion is being investigated in a wide socio-cultural perspective, as well as numerous research approaches to this phenomenon are being analyzed. However, there are still undecided questions, like questions on the influence of religious practice on subjectivity, and the «mechanism» of religious conversion. How to explain the fact of sudden for no reason at all turn to a religion? And how to explain that a believer becomes a new man? The analysis is based on a pragmatic approach, implemented by W. James in «The Varieties of Religious Experience» (lectures IXth-Xth, «Conversion»). Key points of W. James, regarding the phenomenon of religious conversion, are summarized as follows. 1) To convert means to experience a change of «permanent center of energy». One «permanent center» is replaced by another, that is, some religious content of psychic life that were on the periphery of consciousness, according to some objective reasons, become central and form a new «permanent center of energy.» 2) Change one other center, or stable transition of the religious content of psychic life from the periphery to the center is partly accountable to consciousness. This means that a person is not an absolute entity in relation to the events of his psychic life. The process of formation of certain contents of the psyche is hidden for him. So, religious conversion belongs to a specific borderline psychic phenomena. Conversion is objective as an event, however it is uncontrolled from the subject’s perspective. 3) Religious conversion is situational: it can occur whether immediately or gradually. The merit of an American pragmatist and philosopher is that he was the first to describe, using a pragmatic methodology, the specificity of religious conversion from the academic point of view. Everything said by James assumes certain understanding of the structure and dynamics of a social subject, who is experiencing religious conversion. Theoretical model of subjectivity, which James based on implicitly, will be discussed in the second part of the article.