This is Craig's Cosmological Theorem
P: Everything that begins to exist has a cause.
Q: The Universe began to exist.
R: Therefore, there is a cause to the universe.
P⊃Q
Q
∴R
Essentially, this is the Theist's argument for God's existence.
But notice, couldn't all three of the above premises be true, without the requirement of God's existence?
The Atheist could argue that God is not a requirement for the above issues.
The truth is, there could be hundreds of causes to the creation of the universe. We just don't know what that cause is for certain.
In this case, the Theist is basically saying...
"We don't know, therefore, God caused the universe."
Which pretty much follows the same logical format as...
