this thread was about whether or not specific DCs should be listed for jump distances.
It hasn't been about that for around 100+ posts, though. I don't think that 3E or 4e style DCs for jump distances would fit with 5e. But this thread has become about when it is uncertain that a character might clear a greater jump distance than that which p 64 of the rules permits, and thats the issue my posts are addressing.
jumping an unusually long distance is a goal that can be achieved with a successful Athletics check, but to make an Athletics check, you need an approach with a reasonable chance of succeeding at that goal. Jumping normally does not, in my assessment, have a reasonable chance of succeeding at jumping an abnormally long distance.
I don't really follow this. The way you jump far is to jump. Even modern long jumpers, with scientific coaching and absolutely ludicrous amounts of drilling, sometimes jump further and sometimes less far. In the context of a D&D adventure, which on the "realism" side involves characters who are not being scientifically coached, and who have much less control over the circumstances of their launch; and which on the "heroic" side are larger-than-life characters attempting dramatic feats of derring-do; it seems that jumping varying distances depending on a mixture of luck and skill would be quite normal.
This goes back to whether p 64 states a law of nature, or a minimum distance which a jumping character is certain to clear. I think the most natural reading, in light of the text on p 59, is the latter.
No, that's a certain outcome. The PC fails to clear that distance.
Yes, I mistyped. But I hope it was clear that I had grasped your position. You think it is certain that - everything else being equal - a 15 STR character will fail to clear 18 feet with a jump. I don't agree. Which is why I think that the difference is not over what is viable, but rather over what is uncertain.
The referenced action declaration is incomplete. It lacks an approach to the goal.
Goal: I want to get from here to there - 18' across a chasm.
Approach: I jump.
Is it certain that the character will make it? No, because the number on the PC sheet next to STR is 15. (Let's skip over the wonkiness that that's not an element of the fiction but an element of the real world.)
Is it certain that the character will not make it? In my view, no: in the fiction, it is quite conceivable that a character's personal best might exceed his/her routine jump; per the rules, p 59 allows that it is possible to jump unusually far, which means that it is not certain that that can't be done.
Therefore a DC is set and a check made. I don't have an intuitive sense of what the DC should be, because I don't have the intuitions of a 5e referee, but it's tempting to say "Medium" DC 15 - that suggests somewhere around a 50%+ chance of clearing the distance, which seems plausible and suitably dramatic.