Vice President Joe Biden laughed a lot during tonight’s vice presidential debate. For an event that started out with a question about the terrorist attack which claimed the lives of four Americans, what exactly did he think was so darn funny?

Twitter has some theories:

Perhaps moderator Martha Raddatz was giving Biden the giggles.

Things did seem to get a bit serious toward the end. Any theories?

Raddatz noted that this was the first time that two Catholics faced each other in a debate, but she wasn’t the only one with religion on her mind. Quite a few tweeters found Biden’s seemingly endless chuckles reminded them of a certain Bible verse.

OK, that might be the one thing that Biden won’t find hilarious tonight.