I'm not at home, so I can't look it up, but I think Colin Fletcher expressed a light philosophy as far back as the original Complete Walker, in the 70's (?):

Take only what you need.
For what you need, take the lightest item you can find that will still do the job reliably.

Or something along those lines.

I think his corollary was something like, "Price be damned." I know he always commented that his car was a rambling wreck (or maybe a Rambler wreck, for all I know), but that he never stepped away from the trailhead with less than the best item he could afford - even if, a few times, it meant gulping hard and forking over the cash. He didn't mean you could buy your way to a light-and-right pack, but rather than settle for a second-rate item simply to save a few bucks, you're better off buying the best you can afford, or maybe even one step better. (I've tried really hard to follow that advice.)

My own part of the light philosophy is not to become too attached to stuff. By that, I mean don't try to replicate your life at home out on the trail. You don't really need to stay connected (lose the cell phone-internet-computer wireless thingy), and you'll survive a weekend without your iPod music fix. GPS is even arguably optional. But there's more. Give up the mandatory coffee, tea, or cocoa fix every morning, and the three hot meals a day (one is plenty.) Once I realized that I didn't need a hot beverage every meal, nor hot breakfast, I eliminated nearly a pound of coffee, tea, and cocoa mixes and half a pound of cookware from my standard weekly load - and found it somewhat liberating to be able to get up, pack, and get going while munching on that breakfast bar.

I even quit taking a camera, and found that I made lighter (and more permanent) images in my mind, because I paid closer attention.

That's the short form on how my own, personal light philosophy developed.