I've long thought of something that I call the "Divine Delegation of Authority Principle." It seems that after Jehovah God brought forth his only-begotten Son, he has always delegated authority to others and thereby acted mediately through agents. In other words, it seems that Jehovah never does hardly anything directly: he effects the divine will through various agents in order to accomplish his purpose. Examples include:
1) Angels and the Egyptian plagues (Ps. 78:49)
2) God transmitting the Jewish law by means of angels (Gal. 3:19; Heb. 2:2)
3) Creating the world through his Son (John 1:1-3; Col. 1:15-17; Heb. 1:2)
4) Transmitting other covenants through angels
5) Resurrecting people through prophets, the apostles or Jesus Christ
The birth of Christ took place through/by means of the holy spirit, a force which has an interesting role in all divine acts.