> Five whys is explicitly depth first search. I didn't say it wasn't depth first so I have no idea what you're responding to with this. Can you point out where

> Five whys is explicitly depth first search. I didn't say it wasn't depth first so I have no idea what you're responding to with this. Can you point out where in my comment I said it wasn't depth first? I just said it's bounded, because it is. Even the link you've posted states that "why?" is only asked 5 times. But even if you take the 5 as suggestive rather than a strict limit, giving a limit (even a soft one) implies a boundary to the search. If it was meant to be unbounded it would just be called "Whys". 5 pushes you beyond the proximate cause and towards the actual root cause (of course, "root cause" is itself a poor phrase as it implies a singular cause that can be addressed to prevent the problem from reoccurring), but then the root cause could be 10 or 20 or 30 whys deep. So unless you go beyond the point suggested by the name and publications about it then you won't find it. ------------ EDIT: I see you edited your comment after I hit reply and didn't mark it as such, good form. Anyways, about it being depth first I'd actually disagree. Even if you believe that it should be taken as an unbounded search (which I also disagree with, obviously, because there are better tools than 5 whys for such a major task) it should not be an unbounded depth first search. That would be a form of malpractice. The more accurate description would be something like iterative deepening. You go down a few layers with something approximating a depth first search, and then you back track and try the other branches. If you go down one rabbit hole arbitrarily deep you may or may not find a causal factor but you will have missed many others along the branches you chose to ignore for the sake of your unbounded depth first search (again, a form of malpractice).