The merciful, compassionate side of God is presented in the Son, not referred to as Jesus because Jesus had not been born at this time in theological history. In Book III, God says that Adam and Eve will fall and must suffer death. However, death can be overcome for humans if someone in Heaven will sacrifice himself to death for Man. The Son says that he will become human and die in order to defeat death. This act clearly defines the Son. He is powerful and brave, merciful, and willing to act to help Mankind. God's duty is to provide justice — the law has been declared. It is the Son who provides mercy to temper justice — the natural law.
The Son's power is also further revealed in Book VI when God decides to end the rebellion of the angels. God sends only the Son in a chariot against Satan and his hosts. The Son by himself is able to defeat the rebellious angels and cast them into Hell. Milton uses the Son as the acting hand of God's decisions.
God also uses the Son as the creator of Earth and the universe around it. Milton connects the Son closely to Mankind by making the Son the creator of the biblical account. Even though Milton refers to the Son as God in Book VII, it is, nonetheless, the Son who, with golden compasses, lays out the universe and creates Earth and Mankind. Once again, the Son carries out God's plan.
Finally, after the fall of Adam and Eve, the Son goes to Earth at God's request and passes judgment on the serpent, Adam, and Eve. Beyond telling the humans what their punishment will be, the Son also pities them and clothes them in skins. God seems to be almost the embodiment of ideas while the Son converts those ideas to actions.
At the end of Paradise Lost, Michael shows Adam a vision of Jesus, who is the Seed that will ultimately destroy Satan. This scene is the obvious close of the story. The Son, becoming human through Jesus, will live and die. Through resurrection from death, he will finally overcome Satan and save man from the results of the fall. If the reader finds God difficult to comprehend, he finds the Son more compassionate and merciful. Through both characters combined, Milton presents a complete picture of God.