A well-stuffed backpack can be very practical, but there are downsides. The first is back-strain. The second is that it's very hard to be cool when you're carrying one. I tend to avoid them for both reasons, but the second downside seems to shed some light on being cool. So here's a half-baked thought or two.

With paradigm cases of coolness, one thing that stands out is a lack of concern. And a lack of concern tends to preclude certain types of action. You might showcase your cool while skateboarding, giving yourself lung cancer (maybe not under that description), or dancing - but if you're standing in line at the bank or running to catch a train, you just can't be king or queen of the cool mountain. The cool sage is above such things, and seems to effortlessly have the basic needs of life met. He or she does simply what he or she wants to do.

A little more needs to be said there. When I'm in line at the bank, I want to be there in some sense, but it's a want that's embedded in some much larger, more complex want. E.g. "I want to be in line because I want to close that stupid account that has that hidden fee that I want to stop paying because I'd rather spend money on cake or the Nature Conservancy than on Citibank." The cool sage's wants are much more straightfoward, and require much less thought. Ms. Cool is skateboarding simply because she wants to skateboard - no further elaboration needed. Mr. Cool is smoking because he feels like a cigarette - no further elaboration needed. Moreover, these are not intense, consuming wants (or so we must think if we're attributing coolness): it's no big deal if the lighter is out of fluid, or the skateboard breaks. (Of course, it gets pretty hard to stay cool if one's wants are continually frustrated)

One thing this means is that if something is mildly unpleasant, the cool person won't be doing it. He or she doesn't have any big plans that require it, and there's nothing he or she wants enough to bother with it. Which brings up the heavy, well-stuffed backpack. Carrying heavy things is mildly unpleasant, and would only (rationally) be done by people whose wants didn't fit the 'cool' schema. If one's toting suchly, one is probably emerged in some larger plan, and doesn't have one's needs effortlessly met. The cool sage could travel, but she wouldn't pack anything, since she'll find whatever she needs when she needs it.

Of course, this all is why genuine, completely cool people are very rare, and are often independently weathly. It's also why they tend to be profoundly boring... or at least that's what we knowlingly non-cool people tell ourselves as we squirm in the consciousness that, much though we loath to admit it and keep buckets of arguments against it, there's something attractive about coolness.