So this presuppositionalist walks into a bar...

So this presuppositionalist walks into a bar and overhears a man ordering a beer.

He asks, "How do you know that beer really exists?"

The man says, "I know it exists the same way I know that the sky is blue. I look at it, and there it is."

Presup. replies, "Apart from belief in the Trinitarian God, the world is unintelligible, and all attempts at understanding are futile, so you can't know that."

"What does Trinitarian mean?"

"It means the one God exists in 3 persons."

"But I can't understand that until after I believe it?"

"Well, every man already believes it, but represses the knowledge."

"So, this 'repressed knowledge' lets me understand what '3' is, but not what 'blue' is?"

"Well, only when I'm using the '3' for evangelistic purposes."