Final answer:
Jesus is described as 'the one and only mediator between God and humanity' because his sacrifice is believed to have restored the relationship between humanity and God that had been damaged by original sin, in accordance with the Christian trinity doctrine. His status as messiah encompasses a spiritual liberation rather than a physical one as expected in Jewish tradition, and his nature is understood to be both divine and human.
Step-by-step explanation:
We describe Jesus as "the one and only mediator between God and humanity" primarily because of the belief central to Christianity that Jesus, by his sacrifice on the cross, reopened the path to communion with God that was obstructed by original sin. This concept is rooted in Christian theology which sees Jesus as part of the divine trinity—the Father, the Son (Jesus Christ), and the Holy Spirit. Jesus is seen as the second Adam, with his mother Mary as the second Eve. They are believed to have rectified the failings introduced by Adam and Eve in the Garden of Eden, offering humanity a chance at eternal life in heaven through faith and forgiveness of sins.
The declaration of Jesus as the messiah is central to Christian belief but differs from Jewish expectation of a political and territorial liberator. Early Christians interpreted the role of the messiah to be one of spiritual salvation, rather than earthly power.
Additionally, debates regarding Jesus's nature—both human and divine—have persisted throughout Christian history. Miracles performed and his role as the son of God are weighed against his human experiences and emotions, such as anger and doubt, thereby exemplifying the unique union of his dual nature.
The conveyance of Jesus's story and teachings was historically augmented by the use of religious imagery, which served to educate the illiterate and reinforce the narratives to all believers. Complex theological concepts and narratives from early Christianity have therefore been communicated through generations using art, oral tradition, and scripture.