Act of vision is an important analogy used to describe the proceeding of the Intellect from the One in the metaphysical system of Plotinus. It implies that the formation of the universal Intellect is achieved through the process of intellectual contemplation of the First principle, the One, when the Intellect receives its independent existence as a separate divine substance. Latin Christian Platonists, Marius Victorinus and St. Augustine of Hippo, borrowed this idea from Plotinus to describe the proceeding of the Son and of the Holy Spirit from the Father. According to Victorinus, the Son is generated from the Father (the pure divine Being) as its primary movement or life, which corresponds to the intellectual vision which has not yet perceived its object; while the Holy Spirit represents a return of this indefinite intellectual vision to the Father, thus constituting the divine Intelligence, or Self-Consciousness. Likewise, St. Augustine views the Son as an act of intellectual vision of the Father, generated in the process of the divine self-knowledge as an “inner word”, or “notion” of the Father, while the Holy Spirit represents an “intention” of divine will, which causes the Father to produce self-knowledge and generate His “inner word”, or “notion of Himself”, and then connects the divine being of the Father with the generated divine self-knowledge (the Son). Thus the doctrine of Plotinus was rethought by both Christian thinkers to serve the needs of the Christian Trinitarian theology as a rational scheme to explain the mystery of the Holy Trinity.