It is certain because it is impossible. -Certum est quia impossibile
If the Tiber rises too high, or the Nile too low, the remedy is always feeding Christians to the lions.
What has Athens to do with Jerusalem.
Now then, you dogs, whom the apostle puts outside and who yelp at the God of truth, let us come to your various questions.
I believe BECAUSE it's impossible.
Truth engenders hatred of truth. As soon as it appears, it is the enemy.