This Advent we’ve made a point to talk a lot about who God is and what kind of life He is calling us to. We’ve made the point that we have a choice to follow God’s will or our own will, to obtain meaning from God or to live without meaning and purpose, because God made everything with meaning and purpose, but without God everything is just the result of a series of accidents. So, how can we be sure that God really exists? Do we just have to take the best guess with no real evidence? 
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            There are two ways to know something: in itself or from its effects. For example, you can know a person because you met them or because you’ve seen the things that they did. St. Thomas Aquinas believes that we cannot know God in Himself, because He is mysterious and out of our reach (He does reveal Himself to us, but this is Revelation, not reason). Therefore, St. Thomas Aquinas argues for the existence of God from His effects, that is, from the world around us.

            First, we have to have a starting point, so we’ll start with something that we can’t prove, but that is obvious and irrefutable. Nothing comes from nothing. To put it another way, you can’t get something from nothing. Everything has a sufficient reason for its existence. This is called, fitting, The Principle of Sufficient Reason. From this assumption, St. Thomas Aquinas has five ways, or arguments, to come to the existence of God. I’ll summarize two of his arguments today, and we’ll come back to the other three another time. Notice that these ways don’t just try to prove that God exists; they also try to tell us something about God. The original text of the Five Ways can be found in St. Thomas Aquinas’ Summa Theologiae, in the third article of the second question of the “Prima Pars.”

            The Argument from Motion begins with the fact that some things in this world are in motion. We know that whatever is moved is moved by something else. For example, in pool the balls move because they are struck by the cue ball. However, the thing that moves the first thing must also be put in motion by something else, just as the cue ball is first put in motion by the pool cue. This cannot go on infinitely, because then there would be no First Mover and therefore no motion. Therefore, it is necessary to arrive at a first mover, put in motion by no other, and this everyone understands to be God.

            The Argument from Causation is similar to the Argument from Motion. Based on the Principle of Sufficient Reason, we know that nothing can cause itself to exist. An oak tree, for example, comes from an acorn, but the acorn must also be planted in good soul and get enough water for an oak tree to grow. These things are all causes of the oak tree. Now, there’s an order to causes. The acorn that grew into the oak tree came from another oak tree, which came from another acorn, and so on. This procession of causes can’t keep going forever. If there is no First Cause, then there can be no subsequent causes, and then nothing would exist. If there was no original acorn or oak tree, then none of the ones that came from it could exist. However, we know that things do exist. Therefore, there must be a First Cause, and this everyone calls God.

            This Friday we’ll celebrate Christmas and the fact that this First Mover and First Cause entered the world as a little baby born to the Blessed Mother. He isn’t only the distant God of the philosophers; He is also fully revealed to us in the person of Our Lord Jesus Christ.

            In the Catechism of the Catholic Church we learn about the Immaculate Conception of the Blessed Virgin Mary, which we celebrate this Tuesday, December 8:

Through the centuries the Church has become ever more aware that Mary, ‘full of grace’ through God, was redeemed from the moment of her conception. That is what the dogma of the Immaculate Conception confesses, as Pope Pius IX proclaimed in 1854: ‘The most Blessed Virgin Mary was, from the first moment of her conception, by a singular grace and privilege of almighty God and by virtue of the merits of Jesus Christ, Saviour of the human race, preserved immune from all stain of original sin’ (CCC 491).
            Original sin isn’t an actual sin that any of us committed; instead, original sin refers to the actual first sin of Adam and Eve, our first parents, who disobeyed God because, in their pride, they listened to the temptation of Satan, “No, you shall not die the death. For God doth know that in what day soever you shall eat thereof, your eyes shall be opened: and you shall be as Gods, knowing good and evil.” The had already been created by God “to our image and likeness,” but they wanted to be like God without God, or to take God’s place in their own lives. The result of this original sin was the death of the life of God in their souls, what the Catechism calls “the grace of original holiness” (CCC 399). 
            As children of Adam and Eve we are born outside of grace and the friendship of God. However, the Son of God, who is “God from God, light from light, true God from true God,” came to restore us to grace and to the friendship and love of God, and He was born of the Blessed Virgin Mary, the Mother of God. The Church Fathers saw Jesus Christ as a new Adam, come to undo the disobedience of Adam through His own obedience to the Cross. In the same way, they saw the Blessed Virgin as a new Eve. 
            St. Irenaeus of Lyons wrote, “And thus also it was that the know of Eve’s disobedience was loosed by the obedience of Mary. For what the virgin Eve had bound through unbelief, this did the virgin Mary set free through faith” (Against Heresies 3, 22, 4).
            Again, St. Aelred wrote, “Once we lay in death, as you know and believe, in sin, in darkness, in misery. In death, because we had lost the Lord; in sin, because of our corruption; in darkness, for we were without the light of wisdom, and thus had perished utterly. But then we were born, far better than through Eve, through Mary the blessed, because Christ was born of her. We have recovered new life in place of sin, immortality instead of mortality, light in place of darkness. She is our mother – the mother of our life, the mother of our incarnation, the mother of our light” (Sermon 20, in Nativitate beatae Mariae).
            The Blessed Virgin was conceived without original sin because she was “full of grace” from the moment of her conception, because she was to carry in her womb the One who would be a blessing to the entire world.
            Finally, as Saint Sophronius wrote “Enclosed within your womb in God himself. He makes his abode in you and comes forth from you like a bridegroom, winning joy for all and bestowing God’s light on all” (Oratio 2, in sanctissimae Deiparae Annuntiatione).