There are many powerful arguments for God’s existence, such as St. Thomas Aquinas’ argument from contingency.

Then there are trickier ones, such as invoking our free will to prove that there must be a creator. This explanation can work, but it does have some pitfalls.

Here’s how to frame (and not frame) the argument from free will when you’re debating an atheist.

Don’t act like the existence of God automatically follows from the existence of free will.
For those who don’t accept God’s existence, it’s easy to account for free will by referencing natural causes through biological evolution. It’s a similar mindset to the scientist who — though witnessing the extraordinary order in creation — thinks that natural explanations suffice in lieu of a creator.

Many atheistic philosophers and scientists have written and lectured extensively on how free will could have arisen without divine guidance. Their arguments are faulty, but be wary of debating them without being able to refute these arguments.

Catholics believe that the Blessed Virgin Mary always remained a virgin. She never had intimate relations with St. Joseph — Jesus being conceived in her womb by the Holy Spirit.

While many Protestants believe in Christ’s miraculous conception, they hold that Mary and Joseph had other children after our Lord was born.

But Scripture, the Church Fathers and even the early Protestant Reformers are against them.

Here’s the evidence that Jesus was indeed Mary’s only child.

The “brothers” of Jesus mentioned in the Gospels are not his blood brothers.
In Matthew 13:55 we read, “Is not this [Jesus] the carpenter’s son? Is not his mother called Mary? And are not his brethren James and Joseph and Simon and Judas?”

Sure sounds like Jesus had siblings!

The first-century Jews used the word “brother” to mean more than blood brothers. It also meant “cousin” and, in some cases, “uncle.” The Hebrew and Aramaic languages don’t have a word for “cousin.”

Scripture confirms that James and Joseph are not Jesus’ blood relatives. In Matthew 27:56, they are identified as the sons of a different Mary than Our Lady.

Among atheists, a popular objection to Christianity is the so-called “dark passages” of the Old Testament, wherein God seems to command the slaughtering of an entire people. Even many Christians are troubled by these passages, which include Deut. 20:16-18:

“But in the cities of these peoples that the Lord your God gives you for an inheritance, you shall save alive nothing that breathes, but you shall utterly destroy them, the Hittites and the Amorites, the Canaanites and the Per′izzites, the Hivites and the Jeb′usites, as the Lord your God has commanded; that they may not teach you to do according to all their abominable practices which they have done in the service of their gods, and so to sin against the Lord your God.”

If our Lord is a God of love, why would He command the killing of an entire people, which seems to include non-combatant children and women?

Here are a few explanations:

1. God has the right to take life. If God has the right to take life, He has the right to deputize others to do so. In other words, He can choose the methods by which He takes life. For example, He sent plagues that probably killed innocent people. He is free to choose the sword as well. While this view is technically correct, it’s probably not the best one to use in a debate with an atheist.