One of the essential characteristics of the early Christian world is its diversity. The 2nd and 3rd centuries were marked by many different Christian groups that often-held contradictory beliefs about God, creation, Jesus, man, and salvation. The dissertation is focused on two Christian groups that confronted each other during that period. The first one is the so-called Great Church - a stream of Christianity that eventually managed to marginalize other (“heretical”) groups and establish itself as an organized community with a set of accepted doctrines, councils, and hierarchy. The second one is the Valentinian Gnostic School which represented a specific and popular combination of classical Gnostic thought, Greek philosophical tradition (especially Platonism), and the Judeo-Christian tradition. Using a heuristic model of social and religious capital, the dissertation analyzes particular features of those two groups and how these features caused the triumph of the Great Church and the marginalization of the Valentinian Gnostic School. This process is placed in the broader cultural framework characterized by the Roman Empire and the Second Temple Judaism. The main thesis of the dissertation can be defined in the following way: Through the development of its own identity (1st – 3rd centuries), the Great Church emerged as a community that possessed a significantly higher rate of both social (e.g. organized charitable activity that was perceived as a great benefactor of stability) and religious (e.g. narrative constructions such as the idea of apostolic succession that helped strengthen the identity of that community) capital than the Valentinian Gnostic School. Apart from the introduction where the basic research questions and goals were presented, I’ve highlighted the present state of research with a specific focus on the overview of socio-historical approaches in the study of early Christianity. In this respect, the second chapter presented the main studies, especially authors such as Shirley Jackson and Shailer Matthews. Moreover, I’ve made numerous references to the influence of Edwin Judge, Wayne Meeks, and Gerd Theissen. Their work on the development of the first Christian community has given us a fruitful land of new directions and theories. Suffice it to say that Theissen’s collection of essays on the apostle Paul and the community in Corinth has lived up to 75 different editions! In the next chapter I’ve given a detailed review of scholarly studies about the relationship between “heresy” and “orthodoxy”. Because the polemics and battles between different Christian groups in the 2nd and 3rd centuries were crucial in the development of the Great Church, it seemed necessary to present the basic models for the understanding of the early Christian world. I’ve emphasized two different paradigms: The so-called classical or ecclesiastical paradigm represented by authors such as Irenaeus and Eusebius and the contemporary paradigm influenced by the work of Walter Bauer. The first breakthrough after Bauer occurred in the 1970s when Helmut Koester and James M. Robinson published a series of articles arguing that the original (or pure) form of Christianity never existed. Their theory, with some slight changes, remains the dominant discourse in discussions about the relationship between “orthodoxy” and “heresy”. In the fourth chapter, I’ve tried to present the basic terminology related to the stream of Christianity that eventually triumphed over other “heretical” groups such as the Valentinian Gnostic School. I’ve rejected the use of the terms “orthodoxy” or “proto-orthodoxy” because they carry both teleological and theological connotations. Even the phrase “normative Christianity”, popularized by Arland J. Hultgreen, was criticized. In contrast to those suggestions, I have accepted the use of the phrase Great Church as the denominator of that stream of Christianity that came to be recognized as the bearer of “orthodoxy”. Given that the development of the relationship between the Great Church and Valentinian Gnostic School was closely related to the wider socio-political context, the fifth and sixth chapters were focused on elucidating the basic features of that context with special interest to Second Temple Judaism and Roman “paganism”. Perhaps the most fruitful result of that discussion is the clear definition of religion that included both the dimension of beliefs and the dimension of social activity. In that sense, the connection between specific theological postulates and the social reality was anticipated both in the Great Church and in Valentinian Gnostic School. Moreover, such a broad definition of religion gives room for all four entities that were a part of the dissertation: Judaism, Roman religion (polytheism), Great Church, and Valentinian Gnostic School. In the seventh chapter, I tried to analyze the basic features of the “partying of the ways” between Judaism and Christianity. In that aspect, it is worth noting that I’ve tried to show that the seed of the new religion appeared very soon after Jesus’ death when his disciples came to believe that he rose. Needless to say, the separation between Judaism and Christianity was a long–term process, and the identity boundaries were not always clearly defined. Guided by the definition of religion mentioned above, the next chapter focused on the development of the identity of the Great Church during the 1st century. Unlike postmodern historians that emphasize radical diversity and the classical (traditional) paradigm that bears a simple picture, I’ve tried to consider all the available data and present a more balanced view. Basing my analysis of Paul’s authentic epistles and the Acts of the Apostles, I’ve argued that during the first decades after Jesus’ death, the theological and social core of the community was formed. Subsequently, this core was crystallized even more during the 2nd and 3rd centuries. By analyzing the Rule of Faith that can justifiably be defined as the basic symbol of ideological unity, the ninth chapter connected the Great Church of the 1st and 2nd centuries. I’ve argued that the Rule of Faith, as the fundamental theological summary of the Church’s faith, can be seen as an example of the creation of identity boundaries. The core of this Rule is in the connection between the historical Jesus (as a man who lived in Palestine at the beginning of the 1st century) and the resurrected Christ (as God’s Son and a special agent in God’s plan of redemption), but also an emphasis on the value of the Old Testament. Beyond the level of this Rule, the Great Church exercised a “field of flexibility”. Furthermore, I’ve argued that the Rule of Faith can be viewed as an example of religious capital because it represented the building block of the Great Church’s identity. This is of particular importance given the fact that Valentinus and his successors never developed anything like the Rule of Faith. After that, the tenth chapter was focused on the Valentinian Gnostic School. First of all, an effort was made to present the essential characteristics of the broader phenomenon called Gnosticism. In that segment, I rejected the radical methodological deconstructions that call for the abandonment of the term “Gnosticism”. Instead, I’ve proposed a convenient way of using “Gnosticisms” (plural) to highlight all the diversity that was still “held” by the common gnostic myth. Moreover, I’ve analyzed the complex problem of the origin of Gnosticism concluding that Gnosticism did not exist in the pre-Christian period. Although it is difficult to locate the specific origin of such a complex phenomenon, recent studies are inclined towards the urban centers of Egypt (e.g. Alexandria) – Valentinus’ home city. Furthermore, in the same chapter, I’ve dealt with the historical Valentinus and his school. As a popular teacher – a philosopher in Rome during the 2nd century, Valentinus was at the head of a specific community that, at first, was still considered to be a part of the Great Church. However, over the next several decades, the basic theological ideas that Valentinus and his successors advocated became a stumbling block in their relationship with the Great Church. The ideological dimension of Valentinus and his followers represents an important starting position in understanding the various aspects of their social activity. The last part of the tenth chapter analyzed the cosmology and soteriology of Valentinus’ followers by consulting Irenaeus’ summary of Ptolemy’s myth and the Tripartite tractate discovered in Nag Hammadi. The latter represents the only comprehensive description of Valentinian gnosis. I’ve put special emphasis on the differences between the two mentioned sources. Those differences (in some aspects important differences) illustrate the constant revision of the Valentinian myth that points to the acute lack of a normative determinant such as the Rule of Faith characteristic of the Great Church. In addition, the last part of the tenth chapter discussed the three-part anthropology of Valentinians that distinguishes people according to the element that dominates them: spirit, soul, and matter. In the eleventh chapter, I analyzed an important example of the religious capital of the Great Church: The emergence and the development of the concept of heresy. Instead of placing this phenomenon in the middle or the end of the 2nd century, I’ve shown that beginnings can be detected much earlier. Paul’s epistles, if we look at them through the lenses of the sociology of deviance, reveal a community that creates normative boundaries and thereby contributes to the formation of its own identity. Through the rhetorical means of exclusion, stigmatization, and stereotyping, Paul participated in the process of establishing norms that later on became an object of distinction between the Great Church and the Valentinian Gnostic School. With the help of such discursive rhetoric, the Great Church was ready to confront Valentinus and his successors. In the twelfth chapter, I directed my attention to the significant example of both the religious and social capital: The hierarchy and the system of organization in the Great Church and the Valentinian Gnostic School. Relying on the social context of the first Christian communities, I’ve argued that the institutionalization of the Great Church was a relatively fast development in which bishops and presbyters had an important role. Valentinian Gnostic School, characterized by a specific type of spirituality, and cosmology (creation of the world and the beginnings of humankind), rejected the traditional social roles of bishops and presbyters. They considered them as antipodes to the classical Gnostic myth that Valentinus and his followers used to adapt the traditional Judeo – Christian beliefs. Consequently, Valentinians represented a conglomeration of disconnected communities whose identity was closely tied to individual teachers and a specific locality. In other words, Valentinians never developed an ideal of a trans-local community similar to that of the Great Church. In this regard, apostolic succession can be seen as an example of religious capital while the system of organization and authority is an example of social capital. Both of these dimensions did not (to that extent) exist within the Valentinian communities. In the thirteenth chapter, I analyzed the view of tradition both in the Great Church and Valentinian Gnostic School. More specifically, I’ve dealt with the differences between the Great Church and the Valentinian Gnostic School regarding their view on the value of the Old Testament and the Jewish tradition. Unlike the Great Church which places a special emphasis on the continuity of the Old Testament and the life of Jesus, the Valentinians argued for a moderate view – between the radical rejection of the Old Testament (e.g. Marcion) and the view of the Great Church. However, in the Greco – Roman society that was characterized by high value placed on the tradition and the customs of ancestors, the perspective of the Great Church represented an important form of religious capital lacking in the Valentinian Gnostic School. In the fourteenth chapter, I focused on the differences between the two groups regarding the principles of ethics and charity. In a nutshell, I’ve argued that the Great Church stood out with a significantly higher level of practical and organized charity that certainly represented an important form of social capital. Finally, in the fifteenth chapter, I discussed missionary activities as a basic prerequisite in the expansion of any religious community. I’ve tried to show that the Great Church exhibited a considerable rate of missionary activity – it was seen as one of the most visible aspects of the social activities of the Great Church. On the other hand, Valentinians never developed that kind of social impulse. Their “missionary program” was limited and primarily focused on the individuals within the Great Church. This was the consequence of a particular (esoteric) approach to religion and spirituality.