Summary: First demonstration of God's existence: Our universe does not have to exist. There was a time when we did not exist and the universe itself had a beginning some 13.7 billion years ago. We know that matter can neither be created nor destroyed. Something must account for the creation of the universe. The universe must have been created a Being that necessarily exists. The Being must also be all-powerful and all-knowing.

Second demonstration of God's existence: The universe is perfectly fine-tuned for the existence of life. If any of the parameters of the universe were even slightly off atoms would not be able to form and life would not exist.

Summary: Once we have determined using reason alone that God exists, that there is only one God, and that God is all-powerful and all-knowing, we can then look at the Jewish/Christian Scriptures and note that the God of reason is also the God of the Bible. We see that the Scriptures are true but that they must be interpreted correctly. The Scriptures are neither to be taken as absolutely literal nor are they to be dismissed as mere myth.
 

Following the Fall of Man, Man and God were in a state of separation. Ancient Man sought to bridge the gap between himself and God by offering up animal sacrifices. Through Moses God instituted the Passover Feast and later the Jewish people offered up sacrifices to God in the Temple.

In His great love, God decided to send His Son (the Second Person of the Trinity) to earth as Jesus Christ. He became the Passover Lamb and died to take away sin and death. This great Sacrifice is offered to the Father in the Holy Sacrifice of the Mass.

Summary: Jesus Christ founded His Church on Peter, the Rock (Matt 16:18), giving him to the power to make infallible declarations regarding faith and morals. This power was passed down through all of the bishops of Rome, down to Pope Francis in our own day. The Apostles were given the power to forgive sins in Christ's name and to celebrate the Mass. This power has been passed down through bishops (and to priests) through Apostolic Succession. In this way, there is an unbroken chain connecting today's ordained ministers in the Catholic Church to the Apostles. Other Christian denominations (Protestants) were started by individuals throughout history and do not have Apostolic Succession.

In Heaven, we do not merely experience perfect human happiness. Because we participate in the very Body and Blood of Christ, the Church is the Bride of Christ and experiences in Heaven a perfect unity with God. In Heaven we enjoy the very Divine Life of God.