Chalcedonianism is a Christian doctrine established by the Council of Chalcedon in 451 AD. It defines the nature of Jesus Christ as being both fully divine and fully human, united in one person without confusion or separation. This belief was a response to various heresies that misrepresented Christ's nature. The Chalcedonian Definition emphasizes that Christ has two natures—one divine and one human—that coexist in a single person. This doctrine became a cornerstone of orthodox Christian theology, influencing many subsequent debates about the nature of Christ and the relationship between humanity and divinity in Christianity.