Valentinus (Gnostic)
Valentinus (also spelled Valentinius) (c.100 - c.160) was the best known and for a time most successful early Christian gnostic theologian. He founded his school in Rome. According to Tertullian, Valentinus was a candidate for bishop of Rome but started his own group when another was chosen.
Valentinus produced a variety of writings, but only fragments survive, largely those embedded in refuted quotations in the works of his opponents, not enough to reconstruct his system except in broad outline. His doctrine is known to us only in the developed and modified form given to it by his disciples. He taught that there were three kinds of people, the spiritual, psychical, and material; and that only those of a spiritual nature (his own followers) received the gnosis (knowledge) that allowed them to return to the divine Pleroma, while those of a psychic nature (ordinary Christians) would attain a lesser form of salvation, and that those of a material nature (pagans and Jews) were doomed to perish.
Valentinus had a large following, the Valentinians. It later divided into an Eastern and a Western or Italian branch. The Marcosians belonged to the Western branch.
Read more about Valentinus (Gnostic): Biography, Valentinianism, Valentinus' Detractors, The Gospel of Truth