"The legitimate powers of government extend to such acts only as are injurious to others. But it does me no injury for my neighbour to say there are twenty gods, or no god. It neither picks my pocket nor breaks my leg."In my opinion, this is a great maxim to live by. Jefferson originally said this in the context of religious liberty; but libertarians like myself tend to generalize it to apply to everything.
What is interesting is that some of Jefferson's religiously orthodox enemies thought this a very dangerous sentiment. On a number of different grounds, spiritual and temporal.
On temporal grounds, one of the critics reasoned if people thought there was no God, they wouldn't just break your leg, but your neck.
I think that's quite melodramatic and mistaken. But even Jefferson thought that belief in a Providence who administers rewards and punishments was not just true but useful for civilizing man.