God can do whatever He wants, right? Well he obviously can’t make a square-triangle or walk through a door and not walk through a door at the same time. In other words, the law of non-contradiction applies as much to God as to us. But can God be forced to do something? Well ordinarily, no.
But here’s one good example to the contrary: Mary.
One apologetic for the Immaculate Conception (which means that Mary was protected from sin at the moment of her conception to the present day) is the simple question: if you had the power to make your mother how ever you wanted, wouldn’t you make her the best you could? We can’t – but since God is all-powerful and all holy, Mary must have been sustained in God’s grace her entire life. It’s a good argument. It’s also supported by the Greek word kecharitomene, a perfect passive participle used in Luke 1:28 to describe Mary as “full of grace”. That word literally means that Mary was always filled with God’s grace, from her conception on.
But the argument, though supported by Scripture, leaves it up to God’s discretion. What if I were to argue that God HAD to preserve Mary from sin? Okay, first off let me say that I’m in no way arguing against God’s free and sovereign will here. What I’m getting at is this: If God promises to make Mary all the things Catholics believe her to be, then He must keep His promise. You may be wondering where in the Gospels God promised us this Immaculate Mother.
It’s not in the four Gospels. It’s not in the New Testament. It’s not even in the prophetic or historical books of the Old Testament.
To find the promise you have to go back to the third chapter of Genesis, when sin enters the world. We all remember that God kicked Adam and Eve out of the Garden, but do we remember what God said to the Devil? Genesis 3:15 is the often called the protoevangelium, or proto/first Gospel, in which God promises to defeat the Devil through a messiah figure. Here’s the verse: “I [God] will put enmity between you [the Devil] and woman, between your offspring [sin and death] and hers [the messiah]. He will crush your head while you strike his heal.”
If you ever wondered why Jesus crushes the head of the snake at the beginning of the Passion of the Christ, that’s why. In the scene, the Devil asks Jesus: “Who are you?” By crushing the head of the snake, Jesus is saying: “I’m the fulfillment of the protoevangelium.” And as you watch the movie, there is great emphasis on Mary, the “woman” referred to in the prophesy. That’s why Jesus is always calling Mary “woman” – not to be derogatory but to refer to her role in the protoevangelium. [And by the way, the striking of the heal in the verse refers to Jesus' passion, death, and resurrection.]
Okay, so God promised Mary. What does that have to do with the Immaculate Conception? Everything. God promised that there would be “enmity between [the Devil] and [Mary].” The word used for this enmity is total, complete, and perfect. According to God’s promise, there could at no time be a lack of enmity between Mary and the Devil. That means no sin, for by sinning Mary would fight for the Devil as his ally.
So God, by freeing binding Himself in promise in Genesis 3:15, HAD to give us the gift of our Immaculate Mother – and what a gift indeed!