Nothing is new under the sun. This is especially true when it comes to Christological errors. Even in the New Testament the people and the Apostles are confronted with Jesus and are mystified by who he is and who he is not. This problem is brought to the fore by Jesus when he asks "Who do people say that I am?" and alternately "Who do you say that I am?" The answers vary. Some think that Jesus is the prophet foretold to usher in the Messianic Age. Some think that he is really John the Baptist or some other Prophet sent to God's chosen people. But the remarkable answer given in faith, given to the first among the apostles by God is when Jesus is called the "Son of God." What a striking revelation! Elsewhere Jesus calls Himself the "Son of Adam" and yet he affirms that he is also "Son of God." And here in lies the problem. These names would seem to be mutually exclusive but yet in Jesus they find a unity. It is in these names that we find the doctrine of the Hypostatic Union, i.e., the unity of the two natures of Christ (human & divine) in the one person of Christ without division, addition, subtraction nor dimishment of either natures. If one is contemplating this mystery about the person of Jesus and not struck by perplexity and awe then there is little hope that the one contemplating this mystery does not suffer from the vice of acadia which is deadly to the souls path toward holiness. But if this mystery is respected for its utter profundity then one cannot help at times but to err on the side of emphasising Christ's humanity or His divinity.
Son of Man
To a first century Jew it would be odd to hear someone refer to himself by the title "son of Man." What was common was the term "son(s) of Abraham" emphasising the relationship of the promise through the covenant between God and His people. But Jesus chooses to use the word Man instead of Abraham. This is an obvious reference to the beginning of Genesis where the Man is created from the earth by God. This word 'adam is in fact not a proper name but a generic word that first means 'Mankind' and is then later applied to the historical man we call Adam (the husband of Eve). What is significant about this is that by calling himself the "Son of Man" Jesus is universalizing himself. He is not only the Son of the Hebrew people (a son of Abraham) but he is a Son of all of humanity and is himself a part of that same humanity in direct relationship to Adam. This is perhaps the clearest image of Jesus that we can gather - his humanity - since it is that which is the most present to us in an empirical way. We have access to this Jesus through our senses and we know good men in our own lives and so it is not a challenge to our human understanding to know about and love Jesus in the flesh.
Son of God
Just as "Son of Man" refers directly to the likeness of Jesus to Adam so too the name "Son of God" demonstrates the same categorical relationship between Jesus and God the Father. A son is begotten of a Father and so too this Son - Jesus - is begotten of the Heavenly Father and he and the Father are one. This is most emphasised by the Gospel of John and especially in the First chapter where Jesus is identified as the Word (Logos) which similar to the use of the word Man also references the beginning of Genesis. Yet, it references the eternity that is before the beginning of time since the Word was indeed with God and was God. This is also evident in the writings of St. Paul where worship is directed toward the person of Jesus. Oddly this would naturally be the notion of Jesus that we as human beings would have the hardest time relating to in an intimate way. Yet, in my experience it is the divinity of Christ that most people seem to reference when they speak about Him or worse yet, they turn Jesus into something ethereal and he becomes almost ghostlike in their imagining of Him. Jesus becomes remote and passionless in the mind of the person contemplating this aspect of Jesus and thus cannot be reconciled with Him being fully Man in all things but sin.
Son of Mary
It is no surprise that in the first few centuries of the Church there was heated debate about who Jesus was. Heated may be too mild of a term considering that in some places there were the equivalent of "gang wars" in the streets between those who held differing theological opinions about the person of Jesus. To help resolve this problem the Church had recourse to another title for Jesus found in Scripture. Jesus is proclaimed as Son of God, he is self identified as the Son of Man and he is recognized by all as the Son of Mary. It is this latter name that holds the key to uniting the two former names. It is for this reason that at the Council of Ephesus the Council Fathers discerned that a solution to the problem of trying to hold together these two seemingly incompatible notions of Jesus was to affirm the title given to Mary as Theotokos - God Barer. If we can view Jesus through the lens of being the Son of Mary then we can make a little more sense out of the mystery of the Hypostatic Union. It is from her pure flesh that the Divine Logos took human nature void of sin and it was in her womb that the uncreated Word of God thus became incarnate and was born into this world for the salvation of our souls. The two natures come together in a single unity in the womb of the Blessed Mother. It is for this reason that devotion to Our Lady has stood for two millennium! It is through her that we are able to better understand Him and thus enter into a authentic relationship with Jesus as He is, who He is. As an ancient hymn recounts: Mary the shrine, Christ the God adored!