I should preface this by stating that I am not now, and will probably never be, a Christian, but that I also am not now, and will probably never be, the kind of person who thinks that theism is the source of all evil and stupidity in the world.
I am posting this because I am sincerely confused about a particular Christian doctrine, and attempts that I have seen to clarify this doctrine just make it seem to vary based on the argument being made, or else to not make much sense. Given the age and centrality of this doctrine, I just don't think that his can be right: hence my question.
It's this: obviously, it would be blasphemous and absurd to claim that God impregnated the Virgin Mary in the way that human beings typically impregnate one another, Zeus-and-Leda style. Nobody accepts this idea. On the other hand, however, Christians ALSO do not believe that Joseph was Jesus's daddy, or that Jesus was an illegitimate child.
The conclusion seems obvious: God was Jesus's Daddy.
There are four problems with this idea that make it seem unmotivated and doctrinally confused to me:
1) Luke's geneaology of Jesus includes Joseph. Why?
2) If Jesus's daddy is God, then Jesus could receive no DNA from a male, human parent. Obviously, God Himself has no DNA. So, umm. . . ?
3) We are told that the Son is one of the three persons of the Godhead, and that all three have existed since time immemorial. Why, then, would the impregnation of Mary be necessary? Hasn't "the Son" always been "the Son," regardless of "blood" relation?
I don't expect to be persuaded that this doctrine is true, and I don't expect anyone reading this to be persuaded that this doctrine is false. I just don't understand how it fits into a Christian worldview, unlike, say, the doctrine of the Resurrection, or Jesus's various miracles, which seem (whether literally true or not) to make perfect Christian sense.
I appreciate any comments or links which are provided.
EDIT, I meant THREE problems, of course, DERP!