Things vs Stuff, Individuals vs Commodities

In thinking about "what is a thing?", I had this brain fart about the dividing line between things that have an individual identity and "commodities" or "substances". That dividing line is between those things that are chosen or manipulated by "amounts" rather than "names". I.E. When you ask for X number of things (a dozen donuts), or Y ounces of stuff (an ounce of prevention ;-) (i.e. mass nouns), instead of asking for "that one" (i.e. using an indexical), you are referring to things that may actually exist as separate things (e.g. pork bellies, batteries, molecules) but they are so similar that we quit referring to individual ones as individuals. EVEN WHEN picking out a single screw from the basket of screws at the hardware store, it doesn't really have an individual identity! We picked "one", not "that one", much less "Joe".
In fact, to give "names" back to things that have become commodities, we resort to assigning serial numbers to make them each unique.

[Ed. Note - 11/21/07: as per my disclaimers, once I start looking for my epiphanies on the net, I find them. E.G. in this case, see "Conceiving of entities as objects and as stuff". Congrats Bruce, you've just discovered that there are mass nouns vs count nouns.]

POSTSCRIPT - >March 11th, 2010

It turns out that our notion of stuff versus things is so intuitive that they are already being processed by different brain parts during visual processing, long before making any "conscious" decision. At http://www.journalofvision.org/4/8/510/ see Cant, J. S., Valyear, K. F., & Goodale, M. A. .. (2004). 'Stuff' versus 'things': Neural processing of the material properties and geometric form of objects in human visual pathways [Abstract]. Journal of Vision, 4(8):510, 510a, http://journalofvision.org/4/8/510/, doi:10.1167/4.8.510.