On other threads we are discussing carrying the necessities. However, Ed brought up a good point... don't forget to bring an active mind as well.
Here is a hypothetical scenario:
You are nearing the end of the third day of a seven day off-trail trek into the backcountry of northern Maine. For once, there are no biting insects. The late-August weather has been so warm you are wearing just shorts and a T-shirt; all the other layers are in your pack in case you need them.
With a sigh of relief, you shrug off your pack and walk about fifty feet away to respond to a call of nature. A loud growl and the sound of fabric tearing catches your attention. A black bear is attacking your pack, ripping it and tossing it from side to side. You watch as the bear drops your pack... over a ledge right into some Class 5 rapids in the river below. The last you see of all your gear is a hint of blue Cordura going over a falls into an inaccessible canyon. The bear wanders away.
You are left with T-shirt, shorts, a bandana, socks, underwear (optional), and a pair of sturdy hiking boots. No hat, that went with the pack. In your pockets you have a comb and a wallet; car keys, map, compass, and cellphone were in the pack. You do, however, have a fixed-blade knife with a three inch high-carbon steel blade.
It is three hours until sunset. You see rain clouds coming your way, but you figure you have two hours before the rain hits. The previous night it was in the low forties, but the rain might keep it warmer. You are on a relatively flat area with scrub third or fourth growth spruce, some white birch, and the river below you.
What is the first thing that you do?