Well, let's get some things cleared up first. What is a survival situation? Well, what does the word survival mean? At least for me it does not mean surviving getting a wee bit lost for a couple of hours and being late for dinner. For me, it means surviving an immediately life threatening situation, which getting a bit lost most certainly isn't. "Real life"? What is that? People in "real life" can find it horribly shocking that they're so lost they have to backtrack a couple of hours and arrive where they intended to arrive only tomorrow morning instead of tonight. Oh the horror. Other people in "real life" can find the previous about as exciting as going to the kitchen for a beer, and would never call that a survival situation.
As I've said numerous times before, and will say again, even though it is painfully obvious to anyone who knows anything, in most situations of any kind (survival or otherwise) a knife is not necessary, or even "needed." Very often a knife would be useful, however. So, yes, I agree with Runningboar that a knife is most often not needed. On the other hand, I typically carry one, because even though it is not needed it is very much useful - convenient. And, because there are those few situations where it is quite necessary, and if I get really unlucky...
I find the list Runningboar presents in his first post, though, a little weird, considering the entire thread was, it seems, started to make the point of knives not being necessary. I mean, if you're going to state that something isn't necessary, one of the worst ways to make your point is to then list items that are just as unnecessary and say that they are somehow preferable and/or more necessary.
I mean, look at it, honestly, from the perspective of an experienced 'woodsman':
1. A detailed plan, with coordinates if possible, and a time schedule, and how long before help is called left with a dependable person before you leave.
This is, arguably, the most unnecessary thing of them all (but this is not to say it isn't very useful, because it in fact can be very useful)! Half the fun of going out into the wild for a whole lot of folks is in not having a schedule or coordinates, or indeed having people know where you are and when you're coming back. And besides, not everyone has dependable persons ready to keep an eye on you. People have survived without detailed plans and schedules for thousands of years.
Another completely unnecessary item, that won't even work in a whole lot of places. Yes, it's useful for emergency communications, but people did manage to survive in the time when these toys did not exist. And still do survive without them, by the way. So, useful yes, necessary no.
3. A map and compass and know how to use it
Unnecessary. If you know your way around the wild, you won't need to carry a map with you (although you will need to look at it at some point before setting out, to actually know what's out there and what to use for navigation, unless you're going to be all exploring), and a compass is just extra weight. Yes, a map and a compass are very useful, and when moving around in a region that I have no experience from, I will make a point of having them with me always. But necessary? No. As for the know how to use maps and compasses, well, know how isn't an item, so it really is not comparable to a knife in my view.
4.The best clothes and shoes/boots you can afford with extra layers in a daypack
More unnecessary stuff, although very useful and highly recommended for obvious reasons.
5. The ability to make fire now
Intensely unnecessary in a lot of warm regions, and in some desolate ones where there literally is nothing to burn except yourself or any gasses and liquids you may bring along with you.
A lot of very experienced woodsmen never carry any extra items for making a fire, nor even intend to make fires at any point. Of course, having the ability to make a fire is certainly useful. It doesn't necessarily require bringing along any items for that purpose, though. If it's simply a skill in primitive firemaking we're speaking of, then it's not an item and cannot be compared to a knife - because you always bring your skills with you, and they don't weigh extra, so you don't have to make choices between bringing the skill of firemaking or bringing the item of a knife.
6. Water and/or a way to purify it
Depending on how long you intend to be out, you can't bring enough water, and depending on where you are, there's no need to purify it chemically, so... yeah, unnecessary, although very useful.
7. Something to use for overhead cover, a siltarp, space balnket, poncho or the like
More unnecessary and relatively heavy stuff. Useful, though, if you feel like carrying it.
8. A signalling device, at the least a whistle, better yet a PLB, flaregun with flares, or a can of orange smoke
So unnecessary it hurts, and will be useful only if things get really crappy - and you shouldn't let them get that way. Sure, can be life savers in certain situations, but then again, so can a lot of other things.
9. A few power bars or the like
Well, if this isn't unnecessary, then I don't know what is. If you like the taste, though...
10. The ability to stay calm and think, mental preparedness
The only thing on the list even approaching being a necessity, and of course, it's not an item, but rather a mental ability, which you can always bring along even if you're hauling the entire Big He-Man Choppers production line with you. (That all, however, isn't to say that I have any problem with your priorities - they're your priorities, and you can make 'em as you please, that's the beauty of things. You're also likely the person who best knows where you will be going and what you'll be doing there, so you're the best person to set those priorities in an educated fashion.)
So... yeah. A lot of things are unnecessary. Actually, I would say that in most situations everything except one suit of decent clothes is unnecessary. Bring your brains and your hands and feet, and something to wear, and most situations are survivable and the situations that absolutely require you to have brought something else with you are a very small minority indeed. But then, woodsloafing in this way isn't any fun - I like to be able to sit by the fire drinking some cold water and eating some good bread.
So what was my point again? Most things are unnecessary most of the time, a lot of things are useful. Knives aren't any different, although they have many more potential uses than perhaps most other items.
