Person

1. If the Son of God existed before His incarnation, how did He manifest Himself before He became a human being?

In the Old Testament the "Angel of the Lord" might have been another term for the "Son of God". He appeared in human form to Abraham and Moses (Gen. 18, Ex. 3 and 33). He was also called the Word of God (John 1) and the Wisdom of God (Proverbs 8, 1 Cor. 1:30). God created the universe through His Word and Wisdom. He was the Mediator between God and man from the beginning (1 Tim. 2:5). In this way God protected sinful man from the devouring holiness of God.

2. Why was Jesus sometimes called the "Son of God" and sometimes the "Son of Man"?

He was both. The eternal Son of God became a human being, the Son of Man, at a certain point in history. In His human nature He would live a perfect life in our place, and in His human nature He would pay our sin-debt in full. His human nature died on the cross, not His divine nature. After three days His divine nature was reunited with His resurrected human nature for ever. He ascended with both to the right hand of the Father.