Consider: I've been talking to a zookeeper about 20 certain bears for
the past hour, and in fact, I'm in the middle of a sentence regarding
them just as we get to a somewhat filthy cage/habitat, in which I see
2 of those 20 bears. I say "take all the bears in the cage to the
infirmary for a checkup, right now". The zookeeper takes the two bears
out of the cage, and begins shutting the door. I stop him, and say
"take ALL the bears in the cage to the infirmary for a checkup". Is
the difference in meaning, and the utility of that difference
apparent? I hope that it is. This is the difference between position 1
and 2, and it's essential in, to give one example, contractual
writing. But really, it's useful anywhere that you want to explicitly
state what you mean, without having the listener guess based on
context (without having context get in the way of clear
communication).