Sorry deviate for the last time. Think this also answer many
recent posts' questions:
http://www.carm.org/creeds/westminster_larger.htm
Question 38:
Why was it requisite that the Mediator should be God?
Answer: It was requisite that the Mediator should be God, that he
might sustain and keep the human nature from sinking under the
infinite wrath of God, and the power of death; give worth and
efficacy to his sufferings, obedience, and intercession; and to
satisfy God's justice, procure his favor, purchase a peculiar
people, give his Spirit to them, conquer all their enemies, and
bring them to everlasting salvation.