> I’m assuming “godless heathens” is used as the usual partly-accurate counterpart to “goddessless Christians.”
How about poly heathens, whether deity or amory?
Pan too!
> But the proper answer to what a godless heathen says in response to the affirmation quoted is “I so affirm.”
Any judge who poses a religious test as a government agent is a crook, and generally one with a bevy of armed thugs at his disposal. As such, the judge belongs in jail. The proper action is for the court to universally use affirmations that don’t include any theology in the guise of legal process.
> single people. From all the pagans I’ve talked to about the oath, it seems that “so help me God” may be TV-ese only-- none of us have actually been in a courtroom where such an oath was taken. I eagerly await any counterexamples of course. 
I’ve found judges in CT and VA, among other places, who routinely use illegal oaths. If I were to just answer “yes” to the deity pledge, I’d figure that was equivalent to not agreeing to much of anything, though the judge might not comprehend his error or penalize the guilty party (himself or his clerk). Alternately, “So fuck you too” might be suitable, which the judge would likely think profaned his god (himself), though since I believe in neither his external (xtian) nor internal (self) deity, couldn’t be profanity from me. AAMOF, none of my gods can be profaned, and so that concept in contract terms or law impresses me as utter BS whoever’s trying to pretend it’s universal to others needs to grow up and buy a clue about. The FU retort would be a comment on how the judge was in contempt of court and should be locked up without trial.
On the actual witness stand, I have said things more like, “yes, except for that deity reference”. The fact that elective judges in rural districts known for being rabid fundies, and non-elective judges in more developed civilization who really ought to be above that crap, are prepared to immediately offer an alternative oath I take to indicate how clearly they KNOW they’ve violated my rights and everyone else’s, merely by creating that situation in the first place.
I wish I had the chance to just say “No” without explanation, but that might take a case where I wanted to be a hostile witness, rather than trying to deal with the corruption of arbitrary judicial discretion less unfavorably.
On the other side of things, were I a juror and a witness declined an illegal oath, I might take that as suggesting the guy took telling the truth more seriously than do most witnesses. MWBAGs (men with badges and guns) I’d find just above mental health delusionals on the scale of witnesses known to lie regularly. A cop cannot do his job and be fully honest, and so it’s only a question of how and in what forms he perjures himself, even if some of that problem comes from corrupt politicians and illegal laws, in turn a problem of corrupt voters.