It's a pretty impressive piece of counter-Catholicism, not atypical of the academic take on faith that Chesterton loved to poke fun at, such as why churches have spires.

There are a few factual issues, such as the Roman belief in an afterlife, with either the Fields of Elysium, the Plain of Asphodel, or Tartarus to be tortured by the Furies until such time as one's debts were paid in full, which sort of gums up "(t)he ... Roman gods could only mess with you in this world".