Theodicy is the arm of Philosophy (of Religion) which historically has attempted to argumentatively prove God’s existence.

These are some of said “attempts” so far:

1. Saint Tomás and Aristotelic Causality:

God is causa sui, id est, cause of Himself.

Everything has a cause. That would have a prior cause, and a prior cause… Ad infinitum.

So he concludes God is the ultimate cause and, cause of Himself.

2. Canterbuty and Ontologic Argument:

The original formulation includes many attacks against athiest and so on… But the argument is neat and follows as goes:

“God is that which bigger cannot be thought. He is also that which bigger cannot be thought, but must exist, for if He didn’t exist there would be a lesser thing, which, for being doted of existence, would be consequently bigger.”

Contraarguments have been made by many, e.g. Inmanuel Kant, but this argument is thought by many to be formally (logically) perfect.

3. Daniel Prior (I got an Ego, hum) and Gnoseologic Argument:

“Consider anything you know. Anything will do. Now consider where you learned it. Now consider where the person that taught it to you learned it.

Necessarily, we’ll come to something which someone knows, but no other person taught them.”

A more poetic formulation is: “All inspiration is of a divine nature.”