What did Nestorius profess about Mary?

Nestorius is known for his view that, while Mary was indeed the mother of Jesus Christ, she should not be referred to as the "Mother of God" (Theotokos). Instead, he argued that she was the "Mother of Christ" (Christotokos), distinguishing between the divine and human natures of Christ. According to Nestorius, the term "Mother of God" implied that Mary was the source of the divine nature of Christ, which he rejected, emphasizing the importance of maintaining the distinction between Christ's two natures—divine and human. This position became a major point of contention leading to the Third Ecumenical Council at Ephesus in 431, which ultimately affirmed the title "Mother of God" for Mary to clarify the nature of Christ as fully divine and fully human in one person. In this way, the assertion that Mary was the "Mother of Christ" but not the "Mother of God" reflects Nestorius's theological stance and the underlying debates of the early Church regarding Christology and Mariology.