The hypostatic union is the Christian doctrine that in the one person of Jesus Christ, there are two natures: fully God and fully human. These natures are united without mixing, changing, or dividing. This means Jesus is completely divine, with all the attributes of God, and completely human, with all the attributes of humanity. This union is essential for our salvation because it means Jesus can truly represent us as a human and save us with divine power. It means that the man from heaven has submitted his human will to God as the last Adam.