The specific character, structure and vocabulary of Victorinus' theological writings show that the texts were strongly influenced by a Greek philosophical source or sources which are not extant and whose identity is unknown. In recent years, some researchers have shown that there are certain parallels between Victorinus' work and Porphyry, or the anonymous Commentary on the Parmenides, or two anonymous authors mentioned in Proclus' Commentary on the Parmenides, or the treatises of Platonizing Sethian Gnostics from Nag Hammadi. However, all existing solutions of the problem of which sources Victorinus used are questionable. Scholars often misinterpret these texts in order to adapt them to their own hypotheses. One of the main mistakes of the researchers dealing with Marius Victorinus consists in failing to clearly distinguish between different metaphysical schemes involved in Victorinus' theological writings. A comparative analysis of individual writings of Victorinus indicates that they make use of three metaphysical concepts which modify the triad being-life-intelligence in three different ways. According to this thesis I will argue that Victorinus used three different but cognate sources stemming from a common intellectual milieu, which was an alternative to the Neoplatonic mainstream. Moreover, the different structure of the metaphysical concepts in Victorinus' theological writings which have certain parallels in the Gnostic treatises Zostrianos, Allogenes and Three Steles of Seth indicates that Victorinus' sources solved the problem of the relationship between the transcendent One and the level of the Intellect or the intelligible being in different ways.