Which Christian thinkers first incorporated Neoplatonism into Christian doctrine?

Early Christian thinkers initially engaged with Middle Platonism rather than Neoplatonism, as the latter emerged later through figures like Plotinus and Porphyry.1

The incorporation of Neoplatonism into Christian doctrine was a gradual process:

• Marius Victorinus: In the second half of the 4th century, this rhetorician utilized ideas approximating Porphyry’s version of Neoplatonism to articulate and defend the doctrine of the Trinity.1
• St. Augustine of Hippo: While his theology remained rooted in Middle Platonic patterns, he was more deeply and directly influenced by Neoplatonism than any of his Western contemporaries. His work, particularly his Trinitarian theology and epistemology of illumination, reflects a profound engagement with Plotinian thought.12
• Pseudo-Dionysius the Areopagite: Flourishing around 500 CE, this mysterious author explicitly synthesized 5th-century Neoplatonism—specifically the system of Proclus—with Christian theology. His writings established a lasting Neoplatonic trend in medieval Christian doctrine, particularly regarding the hierarchical structure of the universe and mystical union with God.13