The group is spending 40-grand on bus ads in Washington that say: "Why believe in a god?
Just be good for goodness' sake."
Fred Edwords is a spokesman for the humanist group.
He says they're trying to reach agnostics, atheists and others who feel a little alone during the holidays.
Edwords adds they're not trying to argue that God doesn't exist but are trying to raise questions.
While the ads are controversial, Washington transit officials note they aren't obscene or pornographic.