Among the philosophers who most influenced Medieval Christian theology whose work provided the inspiration for stained glass windows in churches is an ancient thinker who was not the person he pretended to be. Dionysius the Areopagite was a minor character in the Book of Acts. In the 5th century, a Christian Neoplatonist impersonated Dionysius as a way to give his philosophical writings the aura of apostolic authority. He was further confused with the patron saint of Paris, a completely different Dionysius or “Denis,” who had been bishop of Paris in the 3rd century. John Hamer of Toronto Centre Place will untangle the histories of the different Dionysiuses and explain the scope and influence of Pseudo-Dionysius’ works.