To Say Something and Not Mean It

What does it mean to say something and not mean it?

I think about this a lot. I first thought about it when I wrote a paper on oath-taking in legal settings for a sociolinguistics class during my masters degree. I didn't and still don't understand how oaths can function without the underlying assumption that we might otherwise be lying all the time, and further, in current society oaths themselves also do not appear to act as the guarantors of truth-telling they once were. In fact, I think we've now bizarrely inverted things; I assume that in a court case where various parties have taken oaths they are more likely to be lying than in everyday, non-oath-underwritten speech.

This notion of making promises or oaths or really any utterances with no intention of truthfulness also came to mind when I thought about musicians who started their careers when they were Christian or otherwise religious and later disassociated themselves from their religious beliefs. Having been a Christian rock fan in the 90s, I've noticed this about a few bands who've reunited recently.  What does it mean when the sing the songs they wrote earlier? Conversely, what does it mean when I sing along with XTC's "Dear God" when I hear it on the radio ("Dear God/ I don't believe in you") even though I do believe in God?

What does it mean when someone promises to bring their child up in the Catholic faith at a baptism, even though they do not consider themselves Catholic and have no intention of doing so?

What does it mean when someone proclaims that they join themselves to another person until death, but at some point -- whether before or after making that proclamation -- decides that they may not or will not be joined to that person until death?

I write about religious things here because religious speech acts seem to be particularly exploitable in this way -- side note: did you know that in the US is not illegal to preach a faith you do not actually believe, thanks to a pretty weird and fascinating Supreme Court case? I mean, I don't know why it would be illegal, but it does seem..bad?

Bourdieu wrote that Protestantism essentially ONLY comprises language, which I think if you're religious you can't really believe, but the fact is, one can say something, something that is presumably meant to only be uttered with sincerity, that appears to have no this-worldly guarantor, and not mean it. Satire exists, of course, but what I'm talking about isn't satire -- it's fulfilling a ritual by making a (potentially) false utterance.

What does it mean to say something and not mean it?