"It's wrong to steal, therefore, one ought not steal."
But, the "therefore" only makes sense here in reference to a separate assumed ought: "one ought not do wrong things."
This assumed ought isn't derived from moral truths (can't derive an ought from an is), it's just sort of pre-supposed. But why?
This ought isn't really argued for, or justified. We just pre-suppose it when stating moral facts ("murder is wrong", "rape is wrong", etc, and therefore one ought not do these wrong things). The italics being a hidden ought which forms the basis of our discussions of what's right and what's wrong. And if it's not there, then who would even care about moral discussions? Whether something is right or wrong wouldn't even matter, because there's nothing at stake It would just be a debate on whether to label a statement "right", or "wrong". A pointless waste of time, without the hidden assumed ought of "one ought not do wrong things".
Does this hidden ought need to be justified? Would there even be any point? Because a psychopath wouldn't be convinced even if you justified it flawlessly.
Why ought I not steal things?
Someone might answer "because stealing is wrong".
But the response here could just be, "and, so what?"
You might then say, "and, one ought not do wrong things."
But why?
There's no real argument for this "one ought not do wrong things." It's just pre-supposed in our discussions of what's right or wrong. These discussions do have something at stake, they're not just about whether to label a statement right or wrong, it's about whether one ought do something or not. Without this pre-supposed 'ought', nothing is at stake. But yet, it itself has no argument or justification for it.
Is there any actual reason or justification for assuming this ought? It seems like it's just something you assume or you don't. And if you don't, then what? The only recourse we have here is threats and punishments, like fines or prison.