This is another document, not part of the Gospel of Truth, but illustrative of the Valentianin effort to convert others. Ptolemy was a student of Valentinus and Flora was presumably a traditional Christian. In his letter to Flora, Ptolemy makes a case for the necessity of reading and understanding the Hebrew scriptures. He explains to Flora that the God of the Hebrew scriptures and creator of the Law of Moses is just, but imperfect.

According to Ptolemy, people have neither understood the Law nor him who ordained it. Ptolemy considers whether Mosaic Law is from God, the Father (who some believe to have created the universe), or the Devil (set upon destruction) and surmises that it is neither. He draws upon the gospels of Matthew and John to make a case for a just God who stands against evil. Having made the point, he explains that it is his job to reveal to her the truth and he can do that because of his understanding of the Hebrew scriptures as well as the words of the Savior. He explained that the teachings of the Hebrew scriptures necessarily had a threefold division of contributions — those from God, those from Moses, and the rest from Jewish elders.

He credits the Savior's teachings for his understanding of the imperfection within the Hebrew scriptures. In the case of divorce, Ptolemy noted that scriptures prohibited the divorce, but a law of Moses permitted it in a case of hard-heartedness. So the Law of Moses created legislation contrary to the law of God. Ptolemy imparts to Flora a belief that the God of the Hebrews and the God that the Savior revealed were not the same. He then embarks upon an esoteric explanation of how the Savior completed the incompleteness and weakness in the law, which was misunderstood and misinterpreted.

Ptolemy offers to send Flora another letter in which he would delve into the topics more deeply. He tells Flora that he has purposefully kept his statements brief but also assures her that he has given her sufficient information so that the seeds may bear fruit (an allusion to the Parable of the Sower). He may have intended to send her a series of letters that explained the Valentinian Gnostic doctrine.

Ptolemy's letter shows his straightforward approach to the subject and the clear and linear flow of logic to his conclusions. The letter is preserved in its entirety by fourth-century church father Epiphanius of Salamis, who quoted it word for word. Epiphanius, who was born a Jew but later converted to Christianity, earned a reputation as a heresiologist who tracked down deviant teachings (teachings at variance with the orthodox doctrine). He spent a period of time in Egypt as a monk and there became aware of popular Valentinian ideas. He founded a monastery in Judea in A.D. 333 and served as the superior for thirty years before becoming the Bishop of Salamis. Ptolemy's Letter to Flora is preserved in his work Panarion (also known as Adversus Haereses).