Since its discovery in the mid-20th century, Nag Hammadi Codex I has been the subject of extensive scholarly interpretation. Among the various possible readings, this paper proposes an understanding of this collection as a document establishing a dividing line between community insiders and outsiders. This distinction is grounded in an ontological and anthropological tripartition (more or less evident across the various writings of the codex) which finds its foundation in a specific cosmological view explaining the organization of the cosmos and the division of humanity into three classes: the pneumatics (the spiritual ones); the psychics; the hylics (the material ones). This tripartite structure serves not only as a principle regulating community membership, but also as an organizational criterion for the internal hierarchy, assigning and defining specific roles and tasks to its members. The last and longest text of Codex I, the so-called Tripartite Tractate, is pivotal in this regard, as it provides a systematic cosmogonic and anthropogonic exposition through which the entire collection can be read. However, the other four writings in the codex also offer evidence supporting this interpretation, since they lay the foundations for the superiority of the pneumatic class and define its responsibilities toward the other human categories. The aim of this paper is, therefore, to highlight the polemical strategies and the dynamics of inclusion and exclusion employed in Nag Hammadi Codex I, demonstrating their role in consolidating a specific internal hierarchical structure.