An argument for the existence of God.
The basis of the argument is that nothing can happen without a cause. There can also not be an endless string of causes. So at some point, there must be an uncaused cause. This cause is God.
Problems with the Cosmological Argument:
The first, and most obvious, problem is the fact that the argument refutes itself. That is, it states that everything has a cause. Then it states that God does not have a cause. Contradiction.
Second, it makes assumptions that may not be valid. Perhaps there are things that can happen without a cause. Perhaps it is possible that there can be a string of uncaused causes.
Note that I didn't create this argument. It's been used by Christian Apologists for years.