To me, the explanation of Jesus the man and Christ, the manifestation of God in Science and Health, is helpful:
"He [Jesus] wrought through the science of being, the example of salvation from sin, sickness, and death, and established the proof that he was Christ, and that Christ is God, the Soul and Life of man." (1st Ed S&H)
a) When we consider God, the Omnipotent, Omnipresent, Omniscient, how can this be contained in anything physical, which by definition is limited, located in one place, etc.?
b) When Jesus said "Before Abraham was I am" He was referring to Christ, not the offspring of Mary. When he said "If ye believe in me, ye shall have eternal life." he again was referring to the Christ, the operation of Principle, not his personality.
c) Today, many are under the delusion that if they profess Jesus, they are saved. "Great! I don't have to change. Just profess!" What utter nonsense, and a denial of all that he taught and lived (consider the Sermon on the Mount - you do not build your house on a rock by professing!!)
Definitions from Science and Health with Key to the Scriptures:
JESUS. The highest human corporeal concept of the divine idea, rebuking and destroying error and bringing to light man's immortality.
CHRIST. The divine manifestation of God, which comes to the flesh to destroy incarnate error.