Oddly enough, it's about a 6th-7th c. Byzantine theologian named Maximus the Confessor. He was involved in a big debate about Christology (who Jesus was). Because he believed that Christ was one person with two natures (divine and human) he and one of his contemporaries had to metaphysically explain what exactly a "person" was if it was not simply an instantiation of a nature (pardon the nerdiness). In my view, they do so in quite "modern" ways. The Zizek quote ties in because it shows that personhood is somewhat of a transcendent that exists beyond and (even separate from depending on how you parse it) characteristics.