The term Gnosticism is used to define a set of religious and philosophical beliefs that developed alongside ancient Christianity, becoming especially popular between the 2nd and the 4th CE. According to Dillon, Gnosticism means “the knowledge of divine mysteries reserved for the elite.” However, the term itself has been used first by modern scholars to summarize the set of philosophies and teachings related to Gnosticism. Ancient gnostikoi did not identify themselves as the representatives of one church, so Gnosticism is rather a school of thought than a specific religion. Although orthodox Christians have always considered Gnosticism to be a dangerous heresy and tried to marginalize its followers, it has a number of common features that connect it to Christianity.
There are several problems that prevented Gnosticism from being adequately reconstructed and interpreted. First of all, there is a lack of genuine Gnostic scriptures, and most of the Gnostic beliefs are known from the polemic works of orthodox Christians who defined it as a threatening heresy. Such judgments were seldom objective as their primary intention was to label all different beliefs as heresy. Dillon indicates the findings of Nag Hammadi library in 1945 as a turning point in a study of Gnosticism, as the collection of ancient scriptures that included some primary Gnostic sources. However, these texts demonstrated another problem of interpretation of Gnosticism as they revealed a variety of the beliefs that some scholars even do not consider as a single philosophy.
Although Gnostic scriptures describe different theologies, some typical features are found in them. The fundamental concept of this belief is a unique ‘hidden’ or secret knowledge available only for the chosen ones that reveal the truth about God, people, and the nature of the world. Dualistic understanding of the world as one consisting of spiritual and material realms is familiar to Christianity, but gnostikoi maximized the opposition between those concepts. Soul, as they believed, was trapped in a lower material world, and its purpose was to escape to the spiritual realm.
Orthodox Christianity had undergone a complex process of establishment during the first centuries of its existence. Dillon states that the religious environment of that period was rather diverse, and Christianity was influenced even by Gnosticism. However, later the ancient orthodox Christians found Gnostic movements to be disrupting to their teaching. By the 2nd century, the fundamental beliefs of Christianity were formed, and Gnosticism posed a threat to them providing a different philosophy. The response of the ancient church was rather harsh, resulting in a series of polemic scriptures that blamed gnostikoi for various sins. Williams defines in Irenaeus’s Against Heresies published in around 180 CE as an “explicit and extensive attack on ‘gnostics.’” Such opposition to Gnosticism and a sharp reaction to it served as the source of identification for the ancient church. Contradicting to Gnosticism, the early Christians were able to find their identity and solidify their beliefs.