The objective existence of God for Catholics is rationally observed in the Mass, in particular the Credo. The Credo describes what God is: One God, the omnipotent father, who created everything, and the Son who is one with God who came down from heaven and became a real person by the Holy Ghost and the Virgin Mary. (No hanky-panky by God, just magic and apparently a little help from Joseph and/or David, and/or God's eternal sperm bank.)Blü:Yes, gods don't have objective existence.
It describes what he did: Was sacrificed to expiate the sins of all men and was resurrected to once again become one God.
It tells why: so all will be resurected to enjoy eternal life.
Then comes the hook: God will judge all, and only those baptized for the forgiveness of sin will get the goodies.
There is nothing imaginary or unreal in that for Catholics. God is more important for them than Blü, J'Carlin, or any other person with the possible exception of the parish priest.