- I'm basing this question on the TV show only, up to the end of Season 6 [so, minor spoiler ahead].
- I'm not using the R+L=J theory, because it's still a theory and not necessary here.
- I didn't read the books, but any information from them that doesn't diverge from the show is welcome !
Facts leading to this question
- Ned said to Jon : "the next time we see each other, we'll talk about your mother" (Season 1 Ep 2)
- As he's described, Ned doesn't take engagements lightly.
- Given the very obvious visual hint (eyes close-up transition), Jon is considered as Lyanna's son (Season 6 Ep 10)
- Lyanna was afraid Robert would kill the baby if he knew (same episode)
Given the possible consequences of revealing who is Jon's mother, probably also his father and the context of his birth, was it wise, honorable, moral from Ned to promise to tell Jon ?
Different approaches that may help address the question
- Honor angle : First, it was very likely Ned and Jon would never see each other again. Ned did intend to tell Jon if they both survived long enough, but that could be after a very long time.
- Moral angle : Ned was probably waiting for Jon to be a "brother of the night's watch" so that the truth would change nothing for Jon's future : you can't leave the night's watch, unless you die first. But isn't that unfair ? Jon might have refused joining the night's watch if he had known, so Ned is depriving Jon from his free will, in a way.
- Wisdom angle : Would Ned have revealed the truth to Jon only ? In fact, even if he tell only to Jon, nothing guaranties that Jon wouldn't tell other people, or that spies would hear and everything would be known. So he must have considered the risk of everybody knowing. Then, how would Robert have reacted ? He couldn't guess Robert would be dead, so it could have been lethal even after all those years, even if Jon "took the black". Similarly, how would Catelyn react ? He didn't trust her for two decades, after all.
As you see, I'm tempted to answer "no it wasn't wise, honorable and moral". Maybe it was just nice, sensible. But I would be interested to read your thoughts about it, in case I missed something or if the books offer different views. Thanks !
As was well explained in the comments, we don't know enough to conclude anything. I can't really change the question to make it answerable.
However, one important thing I overlooked is that Ned had to tell Jon from another moral perspective : not intending to tell would have been worse than just ignoring Jon's hope to know. This morality aspect is probably what motivated Ned's decision as Mooz proposed in the comments. Even if it was risky and a bit dishonest, Jon deserved to hope he would know.
Also, from a psychological point of view, promises like that tend to create a link between characters, and could make them a bit stronger in life. Like if it were a self-realizing prophecy.
However, from a point of view outside of the story evoked by Ber in comments, these kind of promises are set up by the author so that readers/viewers would be even more chocked in the case one of the characters dies. One could say ironically "No, Ned wasn't wise because making such a promise had him killed by the author". But I'm relieved to notice that there are cases where it doesn't happen. (example of Sansa saying to LittleFinger "I expect I'll be a married woman by the time you return")