"Pseudo-Dionysius the Areopagite" is the name scholars have given to an anonymous theologian and philosopher of the 5th century, who wrote a collection of books (Corpus Areopagiticum ) falsely ascribed to the Dionysius mentioned in Acts 17:34. He was commonly believed to be this Dionysius, because he himself wrote as if he were, using the name and claimed aquantance with biblical characters. Georgian Academician Shalva Nutsubidze and Belgian Professor Ernest Honigmann were authors of a theory identitifying the "Pseudo-Dionysius the Areopagite" with Peter the Iberian.
His works show strong Neo-Platonic influence, (especially Proclus, which proves he wrote no earlier than the 5th century), as well as influence from Saint Clement of Alexandria, the Cappadocian Fathers, Origen, and others.
The liturgical references in his writings also date his corpus past the 4th century.
He appeared to have belonged to the group which attempted to form a compromise position between Monophysitism and the orthodox teaching. It also appears that the author lies in the course of his writings, implying that he had written many more works and quoting from his fictitious other works. His writings first appeared in the 5th century, and were used by Monophysites to back up parts of their arguments. Gradually however they began to be accepted by other church theologians as well. They grew to be extremely popular amongst theologians in the middle ages, but debates over the authenticity of his works began in the Renaissance.
Pierre Abélard, the 12th century theologian and philosopher, after his unfortunate experience with Heloise, became a Benedictine monk at Saint Denis. Around 1120 he was convicted of teaching Sabellianism and expelled for a short time. Upon his return around 1121, he turned his attention to the story of their patron saint, and disentangled the three Dionysiuses. The monks were offended, and Abelard did not remain long at Saint-Denis. The great monastery of Saint Denis just north of Paris claimed to have the relics - the mortal remains - of Dionysius (Dionysius = Denys = Denis = Dennis). However, there are at least three Dionysii involved:
Two of the three men, of course, were legitimately named "Dionysius," which was not an uncommon Greek name. The monastery of St-Denis cheerfully conflated the three. They had a good Greek edition of Pseudo-Dionysius's works given to them by Charles the Bald, which was translated into Latin by John Scotus Eriugena in the late 9th century. This translation widely popularized both Pseudo-Dionysius' Neo-Platonism and his explanation of the angels.
It was around 1500 that Lorenzo Valla did much to establish that the "Pseudo-Dionysius" of the 5th Century could not have been St Paul's convert, though he was unable to identify the actual historical author.